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SubjectRe: [PATCH] locking: Add __lockfunc to slow path functions
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On 8/9/22 17:13, Namhyung Kim wrote:
> Hello,
>
> On Tue, Aug 9, 2022 at 8:05 AM Waiman Long <longman@redhat.com> wrote:
>> On 8/8/22 13:59, Namhyung Kim wrote:
>>> So that we can skip the functions in the perf lock contention and other
>>> places like /proc/PID/wchan.
>>>
>>> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
>>> ---
>>> kernel/locking/qrwlock.c | 4 ++--
>>> kernel/locking/qspinlock.c | 2 +-
>>> 2 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
>>> index 2e1600906c9f..d2ef312a8611 100644
>>> --- a/kernel/locking/qrwlock.c
>>> +++ b/kernel/locking/qrwlock.c
>>> @@ -18,7 +18,7 @@
>>> * queued_read_lock_slowpath - acquire read lock of a queued rwlock
>>> * @lock: Pointer to queued rwlock structure
>>> */
>>> -void queued_read_lock_slowpath(struct qrwlock *lock)
>>> +void __lockfunc queued_read_lock_slowpath(struct qrwlock *lock)
>>> {
>>> /*
>>> * Readers come here when they cannot get the lock without waiting
>>> @@ -63,7 +63,7 @@ EXPORT_SYMBOL(queued_read_lock_slowpath);
>>> * queued_write_lock_slowpath - acquire write lock of a queued rwlock
>>> * @lock : Pointer to queued rwlock structure
>>> */
>>> -void queued_write_lock_slowpath(struct qrwlock *lock)
>>> +void __lockfunc queued_write_lock_slowpath(struct qrwlock *lock)
>>> {
>>> int cnts;
>>>
>>> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
>>> index 65a9a10caa6f..2b23378775fe 100644
>>> --- a/kernel/locking/qspinlock.c
>>> +++ b/kernel/locking/qspinlock.c
>>> @@ -313,7 +313,7 @@ static __always_inline u32 __pv_wait_head_or_lock(struct qspinlock *lock,
>>> * contended : (*,x,y) +--> (*,0,0) ---> (*,0,1) -' :
>>> * queue : ^--' :
>>> */
>>> -void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
>>> +void __lockfunc queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
>>> {
>>> struct mcs_spinlock *prev, *next, *node;
>>> u32 old, tail;
>>
>> For completeness, I think you should also add it to the
>> __pv_queued_spin_unlock() and __pv_queued_spin_unlock_slowpath()
>> function in kernel/locking/qspinlock_paravirt.h. Perhaps even the
>> assembly code in arch/x86/include/asm/qspinlock_paravirt.h.
> Thanks for your comment. I'm not sure about the asm part, will this be enough?
>
> --- a/arch/x86/include/asm/qspinlock_paravirt.h
> +++ b/arch/x86/include/asm/qspinlock_paravirt.h
> @@ -36,7 +36,7 @@ PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath);
> * rsi = lockval (second argument)
> * rdx = internal variable (set to 0)
> */
> -asm (".pushsection .text;"
> +asm (".pushsection .spinlock.text;"
> ".globl " PV_UNLOCK ";"
> ".type " PV_UNLOCK ", @function;"
> ".align 4,0x90;"
>
That is what I meant. However, you should also a comment saying that the
use of .spinlock.text section is equivalent to the use of __lockfunc on
an equivalent C function to make it clear. Also add the __lockfunc to
the pseudo code in the comment section.

Cheers,
Longman

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