5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: John Stultz <jstultz@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Signed-off-by: John Stultz <jstultz@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20240709060831.495366-1-jstultz@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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);
}
--
2.43.0
