Peter Daifuku c58029ad24 gpu: nvgpu: fix race for nvgpu_thread_stop ...

The pmu init thread typically returns immediately
without calling nvgpu_thread_should_stop().

pmu_pg_kill_task() checks if the thread is running, and
if it is, calls nvgpu_thread_stop().

However, there's a race condition where the init thread could
have exited between the time that kill_task() checked the
running flag and the time we actually stop the thread, leading
to a kernel crash.

Fix this by making the running flag in the nvgpu_thread struct
atomic. Both the thread proxy function and the thread_stop()
function will set the flag to false.

In the case of nvgpu_thread_proxy(), if the flag is already false,
then nvgpu_thread_stop() has already reset it, at which point we
just wait for nvgpu_thread_should_stop() to return true.

In the case of nvgpu_thread_stop(), if the flag is already false,
then the thread proxy function has already exited, and there is
nothing more to do.

Bug 2591298

Change-Id: I9ba6b63c30a5c3e1df11e790094836b44373122b
Signed-off-by: Peter Daifuku <pdaifuku@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/2230358
GVS: Gerrit_Virtual_Submit
Reviewed-by: Thomas Fleury <tfleury@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

2020-12-15 14:10:29 -06:00

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