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Message-ID: <CAMuHMdX+mpc5++8h4oM98FTPAdV-c8TzscTQA095Wzssae6amg@mail.gmail.com>
Date: Sun, 3 Mar 2024 17:11:02 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Waiman Long <longman@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Arnd Bergmann <arnd@...db.de>,
linux-sh@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-s390 <linux-s390@...r.kernel.org>
Subject: Re: [PATCH/RFC] locking/spinlocks: Make __raw_* lock ops static
Hi Waiman,
CC s390
On Sun, Mar 3, 2024 at 5:25 AM Waiman Long <longman@...hat.com> wrote:
> On 3/1/24 15:43, Geert Uytterhoeven wrote:
> > sh/sdk7786_defconfig (CONFIG_GENERIC_LOCKBREAK=y and
> > CONFIG_DEBUG_LOCK_ALLOC=n):
> >
> > kernel/locking/spinlock.c:68:17: warning: no previous prototype for '__raw_spin_lock' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:80:26: warning: no previous prototype for '__raw_spin_lock_irqsave' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:98:17: warning: no previous prototype for '__raw_spin_lock_irq' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:103:17: warning: no previous prototype for '__raw_spin_lock_bh' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:68:17: warning: no previous prototype for '__raw_read_lock' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:80:26: warning: no previous prototype for '__raw_read_lock_irqsave' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:98:17: warning: no previous prototype for '__raw_read_lock_irq' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:103:17: warning: no previous prototype for '__raw_read_lock_bh' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:68:17: warning: no previous prototype for '__raw_write_lock' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:80:26: warning: no previous prototype for '__raw_write_lock_irqsave' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:98:17: warning: no previous prototype for '__raw_write_lock_irq' [-Wmissing-prototypes]
> > kernel/locking/spinlock.c:103:17: warning: no previous prototype for '__raw_write_lock_bh' [-Wmissing-prototypes]
> >
> > Fix this by making the __raw_* lock ops static.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > ---
> > Compile-tested only.
> >
> > Is SH really the only SMP platform where CONFIG_GENERIC_LOCKBREAK=y?
> > ---
> > kernel/locking/spinlock.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
> > index 8475a0794f8c5ad2..7009b568e6255d64 100644
> > --- a/kernel/locking/spinlock.c
> > +++ b/kernel/locking/spinlock.c
> > @@ -65,7 +65,7 @@ EXPORT_PER_CPU_SYMBOL(__mmiowb_state);
> > * towards that other CPU that it should break the lock ASAP.
> > */
> > #define BUILD_LOCK_OPS(op, locktype) \
> > -void __lockfunc __raw_##op##_lock(locktype##_t *lock) \
> > +static void __lockfunc __raw_##op##_lock(locktype##_t *lock) \
> > { \
> > for (;;) { \
> > preempt_disable(); \
> > @@ -77,7 +77,7 @@ void __lockfunc __raw_##op##_lock(locktype##_t *lock) \
> > } \
> > } \
> > \
> > -unsigned long __lockfunc __raw_##op##_lock_irqsave(locktype##_t *lock) \
> > +static unsigned long __lockfunc __raw_##op##_lock_irqsave(locktype##_t *lock) \
> > { \
> > unsigned long flags; \
> > \
> > @@ -95,12 +95,12 @@ unsigned long __lockfunc __raw_##op##_lock_irqsave(locktype##_t *lock) \
> > return flags; \
> > } \
> > \
> > -void __lockfunc __raw_##op##_lock_irq(locktype##_t *lock) \
> > +static void __lockfunc __raw_##op##_lock_irq(locktype##_t *lock) \
> > { \
> > _raw_##op##_lock_irqsave(lock); \
> > } \
> > \
> > -void __lockfunc __raw_##op##_lock_bh(locktype##_t *lock) \
> > +static void __lockfunc __raw_##op##_lock_bh(locktype##_t *lock) \
> > { \
> > unsigned long flags; \
> > \
>
> This may not work if CONFIG_GENERIC_LOCKBREAK is defined. We had been
sdk7786_defconfig sets CONFIG_GENERIC_LOCKBREAK=y?
FTR, I checked all defconfigs, and it's set in three of them:
- s390/debug_defconfig
- sh/sdk7786_defconfig
- sh/shx3_defconfig
However, the first one has CONFIG_DEBUG_LOCK_ALLOC=y, so the issue
does not trigger there (but see below).
> talking about taking out CONFIG_GENERIC_LOCKBREAK before. See the thread
> in [1]. However, we didn't proceed further at that time as we weren't
> totally sure if there were still some configurations that required
> CONFIG_GENERIC_LOCKBREAK.
>
> [1] https://lore.kernel.org/lkml/20211022120058.1031690-1-arnd@kernel.org/
>
> Anyway, without taking out CONFIG_GENERIC_LOCKBREAK, the proper way to
> fix this issue is probably to declare the proper function prototypes in
> include/linux/rwlock_api_smp.h and include/linux/spinlock_api_smp.h when
> CONFIG_GENERIC_LOCKBREAK is defined.
What is the point of adding function prototypes to header files if the
functions don't seem to be called outside kernel/locking/spinlock.c?
Or is that part of the breakage?
I do not have an sdk7786 or shx3, so I do not know if the kernel
actually boots/works.
The warnings are also seen with s390/debug_defconfig after changing
CONFIG_DEBUG_LOCK_ALLOC=n
CONFIG_DEBUG_WW_MUTEX_SLOWPATH=n
CONFIG_LOCK_STAT=n
CONFIG_PROVE_LOCKING=n
Probably that is the easiest config to test on actual hardware?
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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