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linux/kernel/vhost_task.c

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vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost: Fix worker hangs due to missed wake up calls We can race where we have added work to the work_list, but vhost_task_fn has passed that check but not yet set us into TASK_INTERRUPTIBLE. wake_up_process will see us in TASK_RUNNING and just return. This bug was intoduced in commit f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression") when I moved the setting of TASK_INTERRUPTIBLE to simplfy the code and avoid get_signal from logging warnings about being in the wrong state. This moves the setting of TASK_INTERRUPTIBLE back to before we test if we need to stop the task to avoid a possible race there as well. We then have vhost_worker set TASK_RUNNING if it finds work similar to before. Fixes: f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression") Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20230607192338.6041-3-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2023-06-07 14:23:38 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost: Fix worker hangs due to missed wake up calls We can race where we have added work to the work_list, but vhost_task_fn has passed that check but not yet set us into TASK_INTERRUPTIBLE. wake_up_process will see us in TASK_RUNNING and just return. This bug was intoduced in commit f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression") when I moved the setting of TASK_INTERRUPTIBLE to simplfy the code and avoid get_signal from logging warnings about being in the wrong state. This moves the setting of TASK_INTERRUPTIBLE back to before we test if we need to stop the task to avoid a possible race there as well. We then have vhost_worker set TASK_RUNNING if it finds work similar to before. Fixes: f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression") Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20230607192338.6041-3-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2023-06-07 14:23:38 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
fork, vhost: Use CLONE_THREAD to fix freezer/ps regression When switching from kthreads to vhost_tasks two bugs were added: 1. The vhost worker tasks's now show up as processes so scripts doing ps or ps a would not incorrectly detect the vhost task as another process. 2. kthreads disabled freeze by setting PF_NOFREEZE, but vhost tasks's didn't disable or add support for them. To fix both bugs, this switches the vhost task to be thread in the process that does the VHOST_SET_OWNER ioctl, and has vhost_worker call get_signal to support SIGKILL/SIGSTOP and freeze signals. Note that SIGKILL/STOP support is required because CLONE_THREAD requires CLONE_SIGHAND which requires those 2 signals to be supported. This is a modified version of the patch written by Mike Christie <michael.christie@oracle.com> which was a modified version of patch originally written by Linus. Much of what depended upon PF_IO_WORKER now depends on PF_USER_WORKER. Including ignoring signals, setting up the register state, and having get_signal return instead of calling do_group_exit. Tidied up the vhost_task abstraction so that the definition of vhost_task only needs to be visible inside of vhost_task.c. Making it easier to review the code and tell what needs to be done where. As part of this the main loop has been moved from vhost_worker into vhost_task_fn. vhost_worker now returns true if work was done. The main loop has been updated to call get_signal which handles SIGSTOP, freezing, and collects the message that tells the thread to exit as part of process exit. This collection clears __fatal_signal_pending. This collection is not guaranteed to clear signal_pending() so clear that explicitly so the schedule() sleeps. For now the vhost thread continues to exist and run work until the last file descriptor is closed and the release function is called as part of freeing struct file. To avoid hangs in the coredump rendezvous and when killing threads in a multi-threaded exec. The coredump code and de_thread have been modified to ignore vhost threads. Remvoing the special case for exec appears to require teaching vhost_dev_flush how to directly complete transactions in case the vhost thread is no longer running. Removing the special case for coredump rendezvous requires either the above fix needed for exec or moving the coredump rendezvous into get_signal. Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Co-developed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-01 13:32:32 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00
vhost_task: Handle SIGKILL by flushing work and exiting Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis <eadavis@qq.com> Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: <tencent_546DA49414E876EEBECF2C78D26D242EE50A@qq.com> Signed-off-by: Mike Christie <michael.christie@oracle.com> Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2024-03-15 19:47:06 -05:00
vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2023-03-10 16:03:30 -06:00