kernel/linux.git/include/linux/dma-resv.h, branch v5.15.209

dma-buf: add dma_resv_for_each_fence_unlocked v8

2025-07-17T16:30:52+00:00

[ Upstream commit c921ff373b469ad7907cde219fa700909f59cac4 ] Abstract the complexity of iterating over all the fences in a dma_resv object. The new loop handles the whole RCU and retry dance and returns only fences where we can be sure we grabbed the right one. v2: fix accessing the shared fences while they might be freed, improve kerneldoc, rename _cursor to _iter, add dma_resv_iter_is_exclusive, add dma_resv_iter_begin/end v3: restructor the code, move rcu_read_lock()/unlock() into the iterator, add dma_resv_iter_is_restarted() v4: fix NULL deref when no explicit fence exists, drop superflous rcu_read_lock()/unlock() calls. v5: fix typos in the documentation v6: fix coding error when excl fence is NULL v7: one more logic fix v8: fix index check in dma_resv_iter_is_exclusive() Signed-off-by: Christian König Reviewed-by: Tvrtko Ursulin (v7) Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-2-christian.koenig@amd.com Stable-dep-of: 2b95a7db6e0f ("dma-buf: fix timeout handling in dma_resv_wait_timeout v2") Signed-off-by: Sasha Levin

: correct a function name in kernel-doc

2021-06-29T16:09:24+00:00

Fix kernel-doc function name warning: ../include/linux/dma-resv.h:227: warning: expecting prototype for dma_resv_exclusive(). Prototype was for dma_resv_excl_fence() instead Fixes: 6edbd6abb783d ("dma-buf: rename and cleanup dma_resv_get_excl v3") Signed-off-by: Randy Dunlap Cc: Sumit Semwal Cc: Christian König Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210628004012.6792-1-rdunlap@infradead.org

dma-buf: drop the _rcu postfix on function names v3

2021-06-06T09:19:51+00:00

The functions can be called both in _rcu context as well as while holding the lock. v2: add some kerneldoc as suggested by Daniel v3: fix indentation Signed-off-by: Christian König Reviewed-by: Jason Ekstrand Acked-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210602111714.212426-7-christian.koenig@amd.com

dma-buf: rename dma_resv_get_excl_rcu to _unlocked

2021-06-06T09:19:30+00:00

That describes much better what the function is doing here. Signed-off-by: Christian König Reviewed-by: Jason Ekstrand Acked-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210602111714.212426-6-christian.koenig@amd.com

dma-buf: rename and cleanup dma_resv_get_list v2

2021-06-06T09:18:19+00:00

When the comment needs to state explicitly that this is doesn't get a reference to the object then the function is named rather badly. Rename the function and use it in even more places. v2: use dma_resv_shared_list as new name Signed-off-by: Christian König Acked-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210602111714.212426-5-christian.koenig@amd.com

dma-buf: rename and cleanup dma_resv_get_excl v3

2021-06-06T09:17:58+00:00

When the comment needs to state explicitly that this doesn't get a reference to the object then the function is named rather badly. Rename the function and use rcu_dereference_check(), this way it can be used from both rcu as well as lock protected critical sections. v2: improve kerneldoc as suggested by Daniel v3: use dma_resv_excl_fence as function name Signed-off-by: Christian König Acked-by: Daniel Vetter Reviewed-by: Jason Ekstrand Link: https://patchwork.freedesktop.org/patch/msgid/20210602111714.212426-4-christian.koenig@amd.com

dma-buf: cleanup dma-resv shared fence debugging a bit v2

2021-06-04T12:04:59+00:00

Make that a function instead of inline. v2: improve the kerneldoc wording as suggested by Daniel Signed-off-by: Christian König Reviewed-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210602111714.212426-3-christian.koenig@amd.com

dma-buf: Use sequence counter with associated wound/wait mutex

2020-07-29T14:14:25+00:00

A sequence counter write side critical section must be protected by some form of locking to serialize writers. If the serialization primitive is not disabling preemption implicitly, preemption has to be explicitly disabled before entering the sequence counter write side critical section. The dma-buf reservation subsystem uses plain sequence counters to manage updates to reservations. Writer serialization is accomplished through a wound/wait mutex. Acquiring a wound/wait mutex does not disable preemption, so this needs to be done manually before and after the write side critical section. Use the newly-added seqcount_ww_mutex_t instead: - It associates the ww_mutex with the sequence count, which enables lockdep to validate that the write side critical section is properly serialized. - It removes the need to explicitly add preempt_disable/enable() around the write side critical section because the write_begin/end() functions for this new data type automatically do this. If lockdep is disabled this ww_mutex lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Acked-by: Daniel Vetter Link: https://lkml.kernel.org/r/20200720155530.1173732-13-a.darwish@linutronix.de

dma-buf: Remove custom seqcount lockdep class key

2020-07-29T14:14:25+00:00

Commit 3c3b177a9369 ("reservation: add support for read-only access using rcu") introduced a sequence counter to manage updates to reservations. Back then, the reservation object initializer reservation_object_init() was always inlined. Having the sequence counter initialization inlined meant that each of the call sites would have a different lockdep class key, which would've broken lockdep's deadlock detection. The aforementioned commit thus introduced, and exported, a custom seqcount lockdep class key and name. The commit 8735f16803f00 ("dma-buf: cleanup reservation_object_init...") transformed the reservation object initializer to a normal non-inlined C function. seqcount_init(), which automatically defines the seqcount lockdep class key and must be called non-inlined, can now be safely used. Remove the seqcount custom lockdep class key, name, and export. Use seqcount_init() inside the dma reservation object initializer. Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Sebastian Andrzej Siewior Acked-by: Daniel Vetter Link: https://lkml.kernel.org/r/20200720155530.1173732-12-a.darwish@linutronix.de

dma-buf: Restore seqlock around dma_resv updates

2019-08-16T11:40:58+00:00

This reverts 67c97fb79a7f ("dma-buf: add reservation_object_fences helper") dd7a7d1ff2f1 ("drm/i915: use new reservation_object_fences helper") 0e1d8083bddb ("dma-buf: further relax reservation_object_add_shared_fence") 5d344f58da76 ("dma-buf: nuke reservation_object seq number") The scenario that defeats simply grabbing a set of shared/exclusive fences and using them blissfully under RCU is that any of those fences may be reallocated by a SLAB_TYPESAFE_BY_RCU fence slab cache. In this scenario, while keeping the rcu_read_lock we need to establish that no fence was changed in the dma_resv after a read (or full) memory barrier. Signed-off-by: Chris Wilson Cc: Chris Wilson Cc: Daniel Vetter Acked-by: Christian König Link: https://patchwork.freedesktop.org/patch/msgid/20190814182401.25009-1-chris@chris-wilson.co.uk