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The reset semaphore protects the scheduler and ring objects from concurrent modification, so taking the write side of it is perfectly valid here. Christian. Am 13.09.21 um 06:42 schrieb Pan, Xinhui: > [AMD Official Use Only] > > yep, that is a lazy way to fix it. > > I am thinking of adding one amdgpu_ring.direct_access_mutex before we issue test_ib on each ring. > ________________________________________ > 发件人: Lazar, Lijo > 发送时间: 2021年9月13日 12:00 > 收件人: Pan, Xinhui; amd-gfx@lists.freedesktop.org > 抄送: Deucher, Alexander; Koenig, Christian > 主题: Re: [PATCH v2] drm/amdgpu: Fix a race of IB test > > > > On 9/13/2021 5:18 AM, xinhui pan wrote: >> Direct IB submission should be exclusive. So use write lock. >> >> Signed-off-by: xinhui pan >> --- >> drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c >> index 19323b4cce7b..be5d12ed3db1 100644 >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c >> @@ -1358,7 +1358,7 @@ static int amdgpu_debugfs_test_ib_show(struct seq_file *m, void *unused) >> } >> >> /* Avoid accidently unparking the sched thread during GPU reset */ >> - r = down_read_killable(&adev->reset_sem); >> + r = down_write_killable(&adev->reset_sem); > There are many ioctls and debugfs calls which takes this lock and as you > know the purpose is to avoid them while there is a reset. The purpose is > *not to* fix any concurrency issues those calls themselves have > otherwise and fixing those concurrency issues this way is just lazy and > not acceptable. > > This will take away any fairness given to the writer in this rw lock and > that is supposed to be the reset thread. > > Thanks, > Lijo > >> if (r) >> return r; >> >> @@ -1387,7 +1387,7 @@ static int amdgpu_debugfs_test_ib_show(struct seq_file *m, void *unused) >> kthread_unpark(ring->sched.thread); >> } >> >> - up_read(&adev->reset_sem); >> + up_write(&adev->reset_sem); >> >> pm_runtime_mark_last_busy(dev->dev); >> pm_runtime_put_autosuspend(dev->dev); >>