linux/include/media/cec.h

599 lines
18 KiB

media: cec: fix a deadlock situation The cec_devnode struct has a lock meant to serialize access to the fields of this struct. This lock is taken during device node (un)registration and when opening or releasing a filehandle to the device node. When the last open filehandle is closed the cec adapter might be disabled by calling the adap_enable driver callback with the devnode.lock held. However, if during that callback a message or event arrives then the driver will call one of the cec_queue_event() variants in cec-adap.c, and those will take the same devnode.lock to walk the open filehandle list. This obviously causes a deadlock. This is quite easy to reproduce with the cec-gpio driver since that uses the cec-pin framework which generated lots of events and uses a kernel thread for the processing, so when adap_enable is called the thread is still running and can generate events. But I suspect that it might also happen with other drivers if an interrupt arrives signaling e.g. a received message before adap_enable had a chance to disable the interrupts. This patch adds a new mutex to serialize access to the fhs list. When adap_enable() is called the devnode.lock mutex is held, but not devnode.lock_fhs. The event functions in cec-adap.c will now use devnode.lock_fhs instead of devnode.lock, ensuring that it is safe to call those functions from the adap_enable callback. This specific issue only happens if the last open filehandle is closed and the physical address is invalid. This is not something that happens during normal operation, but it does happen when monitoring CEC traffic (e.g. cec-ctl --monitor) with an unconfigured CEC adapter. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v5.13 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
2021-12-01 13:41:26 +01:00
media: cec: fix a deadlock situation The cec_devnode struct has a lock meant to serialize access to the fields of this struct. This lock is taken during device node (un)registration and when opening or releasing a filehandle to the device node. When the last open filehandle is closed the cec adapter might be disabled by calling the adap_enable driver callback with the devnode.lock held. However, if during that callback a message or event arrives then the driver will call one of the cec_queue_event() variants in cec-adap.c, and those will take the same devnode.lock to walk the open filehandle list. This obviously causes a deadlock. This is quite easy to reproduce with the cec-gpio driver since that uses the cec-pin framework which generated lots of events and uses a kernel thread for the processing, so when adap_enable is called the thread is still running and can generate events. But I suspect that it might also happen with other drivers if an interrupt arrives signaling e.g. a received message before adap_enable had a chance to disable the interrupts. This patch adds a new mutex to serialize access to the fhs list. When adap_enable() is called the devnode.lock mutex is held, but not devnode.lock_fhs. The event functions in cec-adap.c will now use devnode.lock_fhs instead of devnode.lock, ensuring that it is safe to call those functions from the adap_enable callback. This specific issue only happens if the last open filehandle is closed and the physical address is invalid. This is not something that happens during normal operation, but it does happen when monitoring CEC traffic (e.g. cec-ctl --monitor) with an unconfigured CEC adapter. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v5.13 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
2021-12-01 13:41:26 +01:00
media: cec: fix a deadlock situation The cec_devnode struct has a lock meant to serialize access to the fields of this struct. This lock is taken during device node (un)registration and when opening or releasing a filehandle to the device node. When the last open filehandle is closed the cec adapter might be disabled by calling the adap_enable driver callback with the devnode.lock held. However, if during that callback a message or event arrives then the driver will call one of the cec_queue_event() variants in cec-adap.c, and those will take the same devnode.lock to walk the open filehandle list. This obviously causes a deadlock. This is quite easy to reproduce with the cec-gpio driver since that uses the cec-pin framework which generated lots of events and uses a kernel thread for the processing, so when adap_enable is called the thread is still running and can generate events. But I suspect that it might also happen with other drivers if an interrupt arrives signaling e.g. a received message before adap_enable had a chance to disable the interrupts. This patch adds a new mutex to serialize access to the fhs list. When adap_enable() is called the devnode.lock mutex is held, but not devnode.lock_fhs. The event functions in cec-adap.c will now use devnode.lock_fhs instead of devnode.lock, ensuring that it is safe to call those functions from the adap_enable callback. This specific issue only happens if the last open filehandle is closed and the physical address is invalid. This is not something that happens during normal operation, but it does happen when monitoring CEC traffic (e.g. cec-ctl --monitor) with an unconfigured CEC adapter. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v5.13 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
2021-12-01 13:41:26 +01:00
media: cec: fix a deadlock situation The cec_devnode struct has a lock meant to serialize access to the fields of this struct. This lock is taken during device node (un)registration and when opening or releasing a filehandle to the device node. When the last open filehandle is closed the cec adapter might be disabled by calling the adap_enable driver callback with the devnode.lock held. However, if during that callback a message or event arrives then the driver will call one of the cec_queue_event() variants in cec-adap.c, and those will take the same devnode.lock to walk the open filehandle list. This obviously causes a deadlock. This is quite easy to reproduce with the cec-gpio driver since that uses the cec-pin framework which generated lots of events and uses a kernel thread for the processing, so when adap_enable is called the thread is still running and can generate events. But I suspect that it might also happen with other drivers if an interrupt arrives signaling e.g. a received message before adap_enable had a chance to disable the interrupts. This patch adds a new mutex to serialize access to the fhs list. When adap_enable() is called the devnode.lock mutex is held, but not devnode.lock_fhs. The event functions in cec-adap.c will now use devnode.lock_fhs instead of devnode.lock, ensuring that it is safe to call those functions from the adap_enable callback. This specific issue only happens if the last open filehandle is closed and the physical address is invalid. This is not something that happens during normal operation, but it does happen when monitoring CEC traffic (e.g. cec-ctl --monitor) with an unconfigured CEC adapter. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v5.13 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
2021-12-01 13:41:26 +01:00
media: cec: fix a deadlock situation The cec_devnode struct has a lock meant to serialize access to the fields of this struct. This lock is taken during device node (un)registration and when opening or releasing a filehandle to the device node. When the last open filehandle is closed the cec adapter might be disabled by calling the adap_enable driver callback with the devnode.lock held. However, if during that callback a message or event arrives then the driver will call one of the cec_queue_event() variants in cec-adap.c, and those will take the same devnode.lock to walk the open filehandle list. This obviously causes a deadlock. This is quite easy to reproduce with the cec-gpio driver since that uses the cec-pin framework which generated lots of events and uses a kernel thread for the processing, so when adap_enable is called the thread is still running and can generate events. But I suspect that it might also happen with other drivers if an interrupt arrives signaling e.g. a received message before adap_enable had a chance to disable the interrupts. This patch adds a new mutex to serialize access to the fhs list. When adap_enable() is called the devnode.lock mutex is held, but not devnode.lock_fhs. The event functions in cec-adap.c will now use devnode.lock_fhs instead of devnode.lock, ensuring that it is safe to call those functions from the adap_enable callback. This specific issue only happens if the last open filehandle is closed and the physical address is invalid. This is not something that happens during normal operation, but it does happen when monitoring CEC traffic (e.g. cec-ctl --monitor) with an unconfigured CEC adapter. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v5.13 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
2021-12-01 13:41:26 +01:00
media: cec: keep track of outstanding transmits I noticed that repeatedly running 'cec-ctl --playback' would occasionally select 'Playback Device 2' instead of 'Playback Device 1', even though there were no other Playback devices in the HDMI topology. This happened both with 'real' hardware and with the vivid CEC emulation, suggesting that this was an issue in the core code that claims a logical address. What 'cec-ctl --playback' does is to first clear all existing logical addresses, and immediately after that configure the new desired device type. The core code will poll the logical addresses trying to find a free address. When found it will issue a few standard messages as per the CEC spec and return. Those messages are queued up and will be transmitted asynchronously. What happens is that if you run two 'cec-ctl --playback' commands in quick succession, there is still a message of the first cec-ctl command being transmitted when you reconfigure the adapter again in the second cec-ctl command. When the logical addresses are cleared, then all information about outstanding transmits inside the CEC core is also cleared, and the core is no longer aware that there is still a transmit in flight. When the hardware finishes the transmit it calls transmit_done and the CEC core thinks it is actually in response of a POLL messages that is trying to find a free logical address. The result of all this is that the core thinks that the logical address for Playback Device 1 is in use, when it is really an earlier transmit that ended. The main transmit thread looks at adap->transmitting to check if a transmit is in progress, but that is set to NULL when the adapter is unconfigured. adap->transmitting represents the view of userspace, not that of the hardware. So when unconfiguring the adapter the message is marked aborted from the point of view of userspace, but seen from the PoV of the hardware it is still ongoing. So introduce a new bool transmit_in_progress that represents the hardware state and use that instead of adap->transmitting. Now the CEC core waits until the hardware finishes the transmit before starting a new transmit. Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Cc: <stable@vger.kernel.org> # for v4.18 and up Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
2018-10-19 03:55:34 -04:00