Re: [PATCH] rqspinlock: Fix order in raw_res_spin_(un)lock_irq to allow schedule

[Gabriele Monaco <gmonaco@redhat.com>]

On Tue, 2026-06-09 at 13:22 +0200, Arnd Bergmann wrote:
> Should this be Cc:stable@vger.kernel.org to get backported?

Not sure if the Fixes: is enough to trigger the automation, I rarely
remember to Cc:stable@vger.kernel.org and they're usually picked.

In case I guess I'd need to re-submit the patch right?

> Did you see this cause measurable performance problems,
> or did you find it through inspection?

I noticed it while debugging an ENOMEM issue in the test_maps BPF
selftest on PREEMPT_RT and this was an obvious cuplrit (irq_work not
scheduled during a stress run). Turns out the problem is still there
after this fix though.

> 
> > Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
> 
> Acked-by: Arnd Bergmann <arnd@arndb.de> # asm-generic

Thanks,
Gabriele

> 
> This should probably get merged through the BPF tree, but I've
> added the kernel/locking maintainers to Cc as well, since I
> feel it's more useful to have them look at it than me.
> 
> Maybe it would be good to update (as a separate patch) the
> MAINTAINERS file so the locking subsystem also includes the
> headers currently missing:
> 
> arch/*/include/asm/*spinlock*.h
> arch/*/include/asm/*rwlock*.h
> include/asm-generic/*spinlock*.h
> include/asm-generic/*rwlock*.h
> 
>        Arnd
> 
> (full patch quoted below)
> 
> > ---
> >  include/asm-generic/rqspinlock.h | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/include/asm-generic/rqspinlock.h 
> > b/include/asm-generic/rqspinlock.h
> > index 151d267a49..4d46643f46 100644
> > --- a/include/asm-generic/rqspinlock.h
> > +++ b/include/asm-generic/rqspinlock.h
> > @@ -243,12 +243,20 @@ static __always_inline void 
> > res_spin_unlock(rqspinlock_t *lock)
> >  	({                                        \
> >  		int __ret;                        \
> >  		local_irq_save(flags);            \
> > -		__ret = raw_res_spin_lock(lock);  \
> > -		if (__ret)                        \
> > +		preempt_disable();                \
> > +		__ret = res_spin_lock(lock);      \
> > +		if (__ret) {                      \
> >  			local_irq_restore(flags); \
> > +			preempt_enable();         \
> > +		}                                 \
> >  		__ret;                            \
> >  	})
> > 
> > -#define raw_res_spin_unlock_irqrestore(lock, flags) ({ 
> > raw_res_spin_unlock(lock); local_irq_restore(flags); })
> > +#define raw_res_spin_unlock_irqrestore(lock, flags) \
> > +	({                                          \
> > +		res_spin_unlock(lock);              \
> > +		local_irq_restore(flags);           \
> > +		preempt_enable();                   \
> > +	})
> > 
> >  #endif /* __ASM_GENERIC_RQSPINLOCK_H */
> > 
> > base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
> > -- 
> > 2.54.0