locking/rwsem: Add __always_inline annotation to __down_write_common() and inlined callers
PATCH RESEND v2 1/1 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.
---
v2:
* Add ack tags & minor tweaks to commit message
--- kernel/locking/rwsem.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
kernel/locking/rwsem.c +3 -3
@@ -1297,7 +1297,7 @@ 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) {int ret =0 ;
@@ -1310,12 +1310,12 @@ static inline int __down_write_common(struct rw_semaphore *sem, int state)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 ); } -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 ); }
Signature · 1 line
2.45.2.803.g4e1b14247a-goog
The following commit has been merged into the locking/core branch of tip:
The following commit has been merged into the locking/core branch of tip:
Commit-ID: e81859fe64ad42dccefe134d1696e0635f78d763 Gitweb: https://git.kernel.org/tip/e81859fe64ad42dccefe134d1696e0635f78d763 Author: John Stultz <[email protected]> AuthorDate: Mon, 08 Jul 2024 23:08:27 -07:00 Committer: Peter Zijlstra <[email protected]> CommitterDate: Tue, 09 Jul 2024 13:26:26 +02:00
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.
--- kernel/locking/rwsem.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
kernel/locking/rwsem.c +3 -3
@@ -1297,7 +1297,7 @@ 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) {int ret =0 ;
@@ -1310,12 +1310,12 @@ static inline int __down_write_common(struct rw_semaphore *sem, int state)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 ); } -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 ); }