From 6aaa06c15d9bf60c96547384e17198c13c87c646 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Fri, 5 Apr 2024 11:05:16 -0700 Subject: [PATCH] FROMLIST: locking/rwsem: Add __always_inline annotation to __down_write_common() and inlined callers 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. Cc: Tim Murray Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: kernel-team@android.com Fixes: c995e638ccbb ("locking/rwsem: Fold __down_{read,write}*()") Reported-by: Tim Murray Acked-by: Waiman Long Change-Id: I72b273149577b8125ea3a5053befbd5cf66bf8ad Signed-off-by: John Stultz Link: https://lore.kernel.org/lkml/20240620174204.1802235-1-jstultz@google.com/ Bug: 332722989 --- v2: * Add ack tags & minor tweaks to commit message --- 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 98ee3906ee8a..15ebac9c85fb 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1385,7 +1385,7 @@ 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))) @@ -1395,12 +1395,12 @@ 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); }