drm/amdgpu/vkms: relax timer deactivation by hrtimer_try_to_cancel
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
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: 84ec374bd580 ("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>