From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
PowerPC email list <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [RFC PATCH powerpc ] Protect smp_processor_id() in arch_spin_unlock_wait()
Date: Thu, 10 Jan 2013 17:02:06 +1100 [thread overview]
Message-ID: <1357797726.4838.89.camel@pasglop> (raw)
In-Reply-To: <1353305799.3694.9.camel@ThinkPad-T5421.cn.ibm.com>
On Mon, 2012-11-19 at 14:16 +0800, Li Zhong wrote:
> This patch tries to disable preemption for using smp_processor_id() in arch_spin_unlock_wait(),
> to avoid following report:
.../...
> diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
> index bb7cfec..7a7c31b 100644
> --- a/arch/powerpc/lib/locks.c
> +++ b/arch/powerpc/lib/locks.c
> @@ -72,8 +72,10 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock)
> {
> while (lock->slock) {
> HMT_low();
> + preempt_disable();
> if (SHARED_PROCESSOR)
> __spin_yield(lock);
> + preempt_enable();
> }
I assume what you are protecting is the PACA access in SHARED_PROCESSOR
or is there more ?
In that case I'd say just make it use local_paca-> directly or something
like that. It doesn't matter if the access is racy, all processors will
have the same value for that field as far as I can tell.
Cheers,
Ben.
next prev parent reply other threads:[~2013-01-10 6:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-19 6:16 [RFC PATCH powerpc ] Protect smp_processor_id() in arch_spin_unlock_wait() Li Zhong
2013-01-10 6:02 ` Benjamin Herrenschmidt [this message]
2013-01-10 7:50 ` Li Zhong
2013-01-10 9:00 ` [PATCH powerpc ] Avoid debug_smp_processor_id() check " Li Zhong
2013-01-24 3:47 ` Benjamin Herrenschmidt
2013-01-24 10:13 ` Li Zhong
2013-01-24 21:44 ` Benjamin Herrenschmidt
2013-01-25 7:51 ` [PATCH v2 powerpc ] Avoid debug_smp_processor_id() check in SHARED_PROCESSOR Li Zhong
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