linux-kernel - Re: [PATCH] locking: Add __lockfunc to slow path functions

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Date:   Tue, 9 Aug 2022 14:13:14 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] locking: Add __lockfunc to slow path functions

Hello,

On Tue, Aug 9, 2022 at 8:05 AM Waiman Long <longman@...hat.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@...nel.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;"