linux-kernel - [RFC PATCH 5/5] Update get_online_cpus() in Documentation/cpu-hotplug.c

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Message-ID: <20071024053907.GE27074@in.ibm.com>
Date:	Wed, 24 Oct 2007 11:09:07 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Rusty Russel <rusty@...tcorp.com.au>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Nathan Lynch <ntl@...ox.com>
Subject: [RFC PATCH 5/5] Update get_online_cpus() in Documentation/cpu-hotplug.c 

Update the documentation for cpu hotplug to reflect the use
of newly added API's get_online_cpus()/put_online_cpus();

Signed-off-by: Gautham R Shenoy <ego@...ibm.com>

---
 Documentation/cpu-hotplug.txt |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Index: linux-2.6.23/Documentation/cpu-hotplug.txt
===================================================================
--- linux-2.6.23.orig/Documentation/cpu-hotplug.txt
+++ linux-2.6.23/Documentation/cpu-hotplug.txt
@@ -109,12 +109,13 @@ Never use anything other than cpumask_t 
 	for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.
 
 	#include <linux/cpu.h>
-	lock_cpu_hotplug() and unlock_cpu_hotplug():
+	get_online_cpus() and put_online_cpus():
 
-The above calls are used to inhibit cpu hotplug operations. While holding the
-cpucontrol mutex, cpu_online_map will not change. If you merely need to avoid
-cpus going away, you could also use preempt_disable() and preempt_enable()
-for those sections. Just remember the critical section cannot call any
+The above calls are used to inhibit cpu hotplug operations. While the
+cpu_hotplug.refcount is non zero, the cpu_online_map will not change.
+If you merely need to avoid cpus going away, you could also use
+preempt_disable() and preempt_enable() for those sections.
+Just remember the critical section cannot call any
 function that can sleep or schedule this process away. The preempt_disable()
 will work as long as stop_machine_run() is used to take a cpu down.
 
-- 
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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