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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@elte.hu>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Li Zefan <lizf@cn.fujitsu.com>
Subject: Re: [RFC][PATCH] tracing/module: Move tracepoint out of module.h
Date: Thu, 29 Mar 2012 06:22:44 +0200	[thread overview]
Message-ID: <1332994964.3402.17.camel@edumazet-laptop> (raw)
In-Reply-To: <87y5snhwwd.fsf@rustcorp.com.au>

Le mercredi 01 février 2012 à 17:18 +1030, Rusty Russell a écrit :

>  
> +void __module_get(struct module *module)
> +{
> +	if (module) {
> +		preempt_disable();
> +		__this_cpu_inc(module->refptr->incs);
> +		trace_module_get(module, _RET_IP_);
> +		preempt_enable();
> +	}
> +}
> +EXPORT_SYMBOL(__module_get);
> +

Hi Rusty

I am wondering why preempt_disable()/preempt_enable() is needed in this
code.

this_cpu_inc(module->refptr->incs) is preempt safe...



diff --git a/kernel/module.c b/kernel/module.c
index 78ac6ec..7dc88b3 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -907,10 +907,8 @@ static struct module_attribute modinfo_refcnt =
 void __module_get(struct module *module)
 {
 	if (module) {
-		preempt_disable();
-		__this_cpu_inc(module->refptr->incs);
+		this_cpu_inc(module->refptr->incs);
 		trace_module_get(module, _RET_IP_);
-		preempt_enable();
 	}
 }
 EXPORT_SYMBOL(__module_get);
@@ -920,15 +918,11 @@ bool try_module_get(struct module *module)
 	bool ret = true;
 
 	if (module) {
-		preempt_disable();
-
 		if (likely(module_is_live(module))) {
-			__this_cpu_inc(module->refptr->incs);
+			this_cpu_inc(module->refptr->incs);
 			trace_module_get(module, _RET_IP_);
 		} else
 			ret = false;
-
-		preempt_enable();
 	}
 	return ret;
 }
@@ -937,15 +931,13 @@ EXPORT_SYMBOL(try_module_get);
 void module_put(struct module *module)
 {
 	if (module) {
-		preempt_disable();
 		smp_wmb(); /* see comment in module_refcount */
-		__this_cpu_inc(module->refptr->decs);
+		this_cpu_inc(module->refptr->decs);
 
 		trace_module_put(module, _RET_IP_);
 		/* Maybe they're waiting for us to drop reference? */
 		if (unlikely(!module_is_live(module)))
 			wake_up_process(module->waiter);
-		preempt_enable();
 	}
 }
 EXPORT_SYMBOL(module_put);



  parent reply	other threads:[~2012-03-29  4:22 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-16 22:57 [PATCH][GIT PULL][v3.3] tracing: Add header wrappers event_headers_start.h and event_headers_end.h Steven Rostedt
2012-01-17  9:54 ` Ingo Molnar
2012-01-17 13:32   ` Steven Rostedt
2012-01-18 12:07     ` Ingo Molnar
2012-01-18 17:56       ` Steven Rostedt
2012-01-22 22:59         ` Rusty Russell
2012-01-26  2:41           ` [RFC][PATCH] tracing/module: Move tracepoint out of module.h Steven Rostedt
2012-01-26  2:45             ` Steven Rostedt
2012-01-26 10:28             ` Ingo Molnar
2012-01-26 13:52               ` Steven Rostedt
2012-01-26 13:55                 ` Ingo Molnar
2012-01-26 14:04                   ` Steven Rostedt
2012-01-26 14:07                     ` Steven Rostedt
2012-01-26 14:36                     ` Steven Rostedt
2012-01-26 18:39                       ` Ingo Molnar
2012-01-27  3:02                         ` Rusty Russell
2012-01-30 11:52                           ` Steven Rostedt
2012-01-30 17:28                             ` Steven Rostedt
2012-01-31  3:58                             ` Rusty Russell
2012-01-31 12:20                               ` Ingo Molnar
2012-01-31 12:50                                 ` Steven Rostedt
2012-02-01  6:48                                   ` Rusty Russell
2012-02-01 13:27                                     ` Steven Rostedt
2012-02-01 13:49                                     ` Ingo Molnar
2012-02-01 14:25                                       ` Steven Rostedt
2012-03-29  4:22                                     ` Eric Dumazet [this message]
2012-03-29  5:24                                       ` Rusty Russell
2012-02-01  1:10                                 ` Rusty Russell
2012-02-01  7:09                                   ` Ingo Molnar
2012-01-30  6:40                       ` Li Zefan
2012-02-17 13:46       ` [tip:perf/core] tracing/softirq: Move __raise_softirq_irqoff() out of header tip-bot for Steven Rostedt

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