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locking/rwsem: Add __always_inline annotation to __down_write_common() and inlined callers

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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 92cc5d00a4 ("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: c995e638cc ("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
This commit is contained in:
John Stultz 2024-07-08 23:08:27 -07:00 committed by Peter Zijlstra
parent 9bc2ff871f
commit e81859fe64
1 changed files with 3 additions and 3 deletions
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6
kernel/locking/rwsem.c
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@ -1297,7 +1297,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
/* /*
* lock for writing * 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)
{ {
int ret = 0; int ret = 0;
@ -1310,12 +1310,12 @@ static inline int __down_write_common(struct rw_semaphore *sem, int state)
return ret; return ret;
} }
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); __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); return __down_write_common(sem, TASK_KILLABLE);
} }