• Christian König's avatar
    drm/amdgpu: fix incorrect mutex usage v3 · e2840221
    Christian König authored
    Before this patch the scheduler fence was created when we push the job
    into the queue, so we could only get the fence after pushing it.
    
    The mutex now was necessary to prevent the thread pushing the jobs to
    the hardware from running faster than the thread pushing the jobs into
    the queue.
    
    Otherwise the thread pushing jobs into the queue would have accessed
    possible freed up memory when it tries to get a reference to the fence.
    
    So what you get in the end is thread A:
    mutex_lock(&job->lock);
    ...
    Kick of thread B.
    ...
    mutex_unlock(&job->lock);
    
    And thread B:
    mutex_lock(&job->lock);
    ....
    mutex_unlock(&job->lock);
    kfree(job);
    
    I'm actually not sure if I'm still up to date on this, but this usage
    pattern used to be not allowed with mutexes. See here as well
    https://lwn.net/Articles/575460/.
    
    v2: remove unrelated changes, fix missing owner
    v3: rebased, add more commit message
    Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
    Reviewed-by: default avatarAlex Deucher <alexander.deucher@amd.com>
    e2840221
gpu_scheduler.h 4.22 KB