linux-kernel - Re: [PATCH v8 4/8] smp: add func to IPI cpus based on parameter func

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Message-Id: <20120208160344.88d187e5.akpm@linux-foundation.org>
Date:	Wed, 8 Feb 2012 16:03:44 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Michal Nazarewicz" <mina86@...a86.com>
Cc:	linux-kernel@...r.kernel.org,
	"Gilad Ben-Yossef" <gilad@...yossef.com>,
	"Chris Metcalf" <cmetcalf@...era.com>,
	"Christoph Lameter" <cl@...ux-foundation.org>,
	"Frederic Weisbecker" <fweisbec@...il.com>,
	"Russell King" <linux@....linux.org.uk>, linux-mm@...ck.org,
	"Pekka Enberg" <penberg@...nel.org>,
	"Matt Mackall" <mpm@...enic.com>,
	"Sasha Levin" <levinsasha928@...il.com>,
	"Rik van Riel" <riel@...hat.com>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Alexander Viro" <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, "Avi Kivity" <avi@...hat.com>,
	"Kosaki Motohiro" <kosaki.motohiro@...il.com>,
	"Milton Miller" <miltonm@....com>
Subject: Re: [PATCH v8 4/8] smp: add func to IPI cpus based on parameter
 func

On Wed, 08 Feb 2012 10:30:51 +0100
"Michal Nazarewicz" <mina86@...a86.com> wrote:

> >  	} while (0)
> > +/*
> > + * Preemption is disabled here to make sure the
> > + * cond_func is called under the same condtions in UP
> > + * and SMP.
> > + */
> > +#define on_each_cpu_cond(cond_func, func, info, wait, gfp_flags) \
> > +	do {						\
> 
> How about:
> 
> 		void *__info = (info);
> 
> as to avoid double execution.

Yup.  How does this look?


From: Andrew Morton <akpm@...ux-foundation.org>
Subject: smp-add-func-to-ipi-cpus-based-on-parameter-func-update-fix

- avoid double-evaluation of `info' (per Michal)
- parenthesise evaluation of `cond_func'

Cc: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: Gilad Ben-Yossef <gilad@...yossef.com>
Cc: Michal Nazarewicz <mina86@...a86.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 include/linux/smp.h |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/include/linux/smp.h~smp-add-func-to-ipi-cpus-based-on-parameter-func-update-fix
+++ a/include/linux/smp.h
@@ -168,10 +168,11 @@ static inline int up_smp_call_function(s
  */
 #define on_each_cpu_cond(cond_func, func, info, wait, gfp_flags)\
 	do {							\
+		void *__info = (info);				\
 		preempt_disable();				\
-		if (cond_func(0, info)) {			\
+		if ((cond_func)(0, __info)) {			\
 			local_irq_disable();			\
-			(func)(info);				\
+			(func)(__info);				\
 			local_irq_enable();			\
 		}						\
 		preempt_enable();				\
_

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