Re: [PATCH v8 1/2] drm/gem: Properly annotate WW context on drm_gem_lock_reservations() error

From: Christian König
Date: Wed Aug 10 2022 - 05:04:42 EST


Am 10.08.22 um 10:33 schrieb Daniel Vetter:
On Wed, 10 Aug 2022 at 08:52, Christian König <christian.koenig@xxxxxxx> wrote:
Am 09.08.22 um 18:44 schrieb Daniel Vetter:
On Tue, Jul 05, 2022 at 01:33:51PM +0200, Christian König wrote:
Am 01.07.22 um 11:02 schrieb Dmitry Osipenko:
Use ww_acquire_fini() in the error code paths. Otherwise lockdep
thinks that lock is held when lock's memory is freed after the
drm_gem_lock_reservations() error. The ww_acquire_context needs to be
annotated as "released", which fixes the noisy "WARNING: held lock freed!"
splat of VirtIO-GPU driver with CONFIG_DEBUG_MUTEXES=y and enabled lockdep.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 7edc3e3b975b5 ("drm: Add helpers for locking an array of BO reservations.")
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
Also added this r-b tag when merging to drm-misc-next-fixes.
IIRC I've already pushed this to drm-misc-fixes with a CC stable tag
about 2 weeks ago.

Please double check, it probably just hasn't come down the stream again yet.
Hm quickly check and I didn't spot it? There's a few patches from
Dmitry in the last few pulls, and some more stuff pending, but not
these two afaics?

Mhm, there is some potential that I wanted to push it but got distracted by the re-occurring drm-tip build breakages.

Anyway what I wanted to say is that this stuff should probably go to drm-misc-fixes with a CC: stable tag :)

Christian.

-Daniel

Christian.

-Daniel

---
drivers/gpu/drm/drm_gem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index eb0c2d041f13..86d670c71286 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1226,7 +1226,7 @@ drm_gem_lock_reservations(struct drm_gem_object **objs, int count,
ret = dma_resv_lock_slow_interruptible(obj->resv,
acquire_ctx);
if (ret) {
- ww_acquire_done(acquire_ctx);
+ ww_acquire_fini(acquire_ctx);
return ret;
}
}
@@ -1251,7 +1251,7 @@ drm_gem_lock_reservations(struct drm_gem_object **objs, int count,
goto retry;
}
- ww_acquire_done(acquire_ctx);
+ ww_acquire_fini(acquire_ctx);
return ret;
}
}