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Guchun Chen 1ac157c8a7 drm/amdgpu/vkms: relax timer deactivation by hrtimer_try_to_cancel 
commit b42ae87a7b upstream.

In below thousands of screen rotation loop tests with virtual display
enabled, a CPU hard lockup issue may happen, leading system to unresponsive
and crash.

do {
	xrandr --output Virtual --rotate inverted
	xrandr --output Virtual --rotate right
	xrandr --output Virtual --rotate left
	xrandr --output Virtual --rotate normal
} while (1);

NMI watchdog: Watchdog detected hard LOCKUP on cpu 1

? hrtimer_run_softirq+0x140/0x140
? store_vblank+0xe0/0xe0 [drm]
hrtimer_cancel+0x15/0x30
amdgpu_vkms_disable_vblank+0x15/0x30 [amdgpu]
drm_vblank_disable_and_save+0x185/0x1f0 [drm]
drm_crtc_vblank_off+0x159/0x4c0 [drm]
? record_print_text.cold+0x11/0x11
? wait_for_completion_timeout+0x232/0x280
? drm_crtc_wait_one_vblank+0x40/0x40 [drm]
? bit_wait_io_timeout+0xe0/0xe0
? wait_for_completion_interruptible+0x1d7/0x320
? mutex_unlock+0x81/0xd0
amdgpu_vkms_crtc_atomic_disable

It's caused by a stuck in lock dependency in such scenario on different
CPUs.

CPU1                                             CPU2
drm_crtc_vblank_off                              hrtimer_interrupt
    grab event_lock (irq disabled)                   __hrtimer_run_queues
        grab vbl_lock/vblank_time_block                  amdgpu_vkms_vblank_simulate
            amdgpu_vkms_disable_vblank                       drm_handle_vblank
                hrtimer_cancel                                         grab dev->event_lock

So CPU1 stucks in hrtimer_cancel as timer callback is running endless on
current clock base, as that timer queue on CPU2 has no chance to finish it
because of failing to hold the lock. So NMI watchdog will throw the errors
after its threshold, and all later CPUs are impacted/blocked.

So use hrtimer_try_to_cancel to fix this, as disable_vblank callback
does not need to wait the handler to finish. And also it's not necessary
to check the return value of hrtimer_try_to_cancel, because even if it's
-1 which means current timer callback is running, it will be reprogrammed
in hrtimer_start with calling enable_vblank to make it works.

v2: only re-arm timer when vblank is enabled (Christian) and add a Fixes
tag as well

v3: drop warn printing (Christian)

v4: drop superfluous check of blank->enabled in timer function, as it's
guaranteed in drm_handle_vblank (Christian)

Fixes: 84ec374bd5 ("drm/amdgpu: create amdgpu_vkms (v4)")
Cc: stable@vger.kernel.org
Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-07-27 08:56:38 +02:00
arch arm64/fpsimd: Ensure SME storage is allocated after SVE VL changes 2023-07-27 08:56:36 +02:00
block blk-crypto: use dynamic lock class for blk_crypto_profile::lock 2023-07-23 13:53:39 +02:00
certs KEYS: Add missing function documentation 2023-04-24 16:15:52 +03:00
crypto crypto: jitter - correct health test during initialization 2023-07-19 16:36:19 +02:00
Documentation media: uapi: Fix [GS]_ROUTING ACTIVE flag value 2023-07-23 13:54:08 +02:00
drivers drm/amdgpu/vkms: relax timer deactivation by hrtimer_try_to_cancel 2023-07-27 08:56:38 +02:00
fs btrfs: fix race between balance and cancel/pause 2023-07-27 08:56:35 +02:00
include fuse: add feature flag for expire-only 2023-07-27 08:56:34 +02:00
init kbuild: Fix CFI failures with GCOV 2023-07-19 16:36:23 +02:00
io_uring io_uring: Fix io_uring mmap() by using architecture-provided get_unmapped_area() 2023-07-27 08:56:31 +02:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel prctl: move PR_GET_AUXV out of PR_MCE_KILL 2023-07-27 08:56:33 +02:00
lib maple_tree: set the node limit when creating a new root node 2023-07-27 08:56:32 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/mlock: fix vma iterator conversion of apply_vma_lock_flags() 2023-07-27 08:56:32 +02:00
net can: bcm: Fix UAF in bcm_proc_show() 2023-07-27 08:56:36 +02:00
rust Rust changes for v6.4 2023-04-30 11:20:22 -07:00
samples samples: ftrace: Save required argument registers in sample trampolines 2023-07-23 13:54:09 +02:00
scripts kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS 2023-07-19 16:37:00 +02:00
security keys: Fix linking a duplicate key to a keyring's assoc_array 2023-07-27 08:56:32 +02:00
sound ALSA: hda/realtek: Enable Mute LED on HP Laptop 15s-eq2xxx 2023-07-27 08:56:32 +02:00
tools selftests: tc: add ConnTrack procfs kconfig 2023-07-27 08:56:37 +02:00
usr initramfs: Check negative timestamp to prevent broken cpio archive 2023-04-16 17:37:01 +09:00
virt KVM: Avoid illegal stage2 mapping on invalid memory slot 2023-06-22 15:14:57 -04:00
.clang-format cxl for v6.4 2023-04-30 11:51:51 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore linux-kselftest-kunit-6.4-rc1 2023-04-24 12:31:32 -07:00
.mailmap mailmap: add entries for Ben Dooks 2023-06-19 13:19:35 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: sctp: move Neil to CREDITS 2023-05-12 08:51:32 +01:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Networking fixes for 6.4-rc8, including fixes from ipsec, bpf, 2023-06-22 17:59:51 -07:00
Makefile Linux 6.4.6 2023-07-24 18:56:41 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.