5.15-stable review patch. If anyone has any objections, please let me know.
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From: John Stultz jstultz@google.com
[ Upstream commit e81859fe64ad42dccefe134d1696e0635f78d763 ]
Apparently despite it being marked inline, the compiler may not inline __down_write_common() which makes it difficult to identify the cause of lock contention, as the wchan of the blocked function will always be listed as __down_write_common().
So add __always_inline annotation to the common function (as well as the inlined helper callers) to force it to be inlined so a more useful blocking function will be listed (via wchan).
This mirrors commit 92cc5d00a431 ("locking/rwsem: Add __always_inline annotation to __down_read_common() and inlined callers") which did the same for __down_read_common.
I sort of worry that I'm playing wack-a-mole here, and talking with compiler people, they tell me inline means nothing, which makes me want to cry a little. So I'm wondering if we need to replace all the inlines with __always_inline, or remove them because either we mean something by it, or not.
Fixes: c995e638ccbb ("locking/rwsem: Fold __down_{read,write}*()") Reported-by: Tim Murray timmurray@google.com Signed-off-by: John Stultz jstultz@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Waiman Long longman@redhat.com Link: https://lkml.kernel.org/r/20240709060831.495366-1-jstultz@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/locking/rwsem.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 4a38d32b89fa3..eca42c14ec09a 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1286,7 +1286,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) /* * lock for writing */ -static inline int __down_write_common(struct rw_semaphore *sem, int state) +static __always_inline int __down_write_common(struct rw_semaphore *sem, int state) { if (unlikely(!rwsem_write_trylock(sem))) { if (IS_ERR(rwsem_down_write_slowpath(sem, state))) @@ -1296,12 +1296,12 @@ static inline int __down_write_common(struct rw_semaphore *sem, int state) return 0; }
-static inline void __down_write(struct rw_semaphore *sem) +static __always_inline void __down_write(struct rw_semaphore *sem) { __down_write_common(sem, TASK_UNINTERRUPTIBLE); }
-static inline int __down_write_killable(struct rw_semaphore *sem) +static __always_inline int __down_write_killable(struct rw_semaphore *sem) { return __down_write_common(sem, TASK_KILLABLE); }