linux-kernel - Re: msgrcv: use freezable blocking call

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Date:	Tue, 31 Mar 2015 14:30:33 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	maninder1.s@...sung.com
Cc:	linux-kernel@...r.kernel.org,
	"yn.gaur@...sung.com" <yn.gaur@...sung.com>,
	"ajeet.y@...sung.com" <ajeet.y@...sung.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Tejun Heo <tj@...nel.org>
Subject: Re: msgrcv: use freezable blocking call


Presumably Peter's review comments for "restart_syscall: use freezable
blocking call" also apply here.

Please send your signed-off-by: for both patches, as detailed in
Documentation/SubmittingPatches section 11, thanks.


From: Yogesh Gaur <yn.gaur@...sung.com>
Subject: ipc/msg.c: use freezable blocking call

Avoid waking up every thread sleeping in a msgrcv call during suspend and
resume by calling a freezable blocking call.  Previous patches modified
the freezer to avoid sending wakeups to threads that are blocked in
freezable blocking calls.

Ref: https://lkml.org/lkml/2013/5/1/424

Backtrace: 
[<c03e3924>] (__schedule+0x0/0x5d8) from [<c03e3f88>] (schedule+0x8c/0x90)
[<c03e3efc>] (schedule+0x0/0x90) from [<c01ef9f8>] (do_msgrcv+0x2e0/0x368)
[<c01ef718>] (do_msgrcv+0x0/0x368) from [<c01efaac>] (SyS_msgrcv+0x2c/0x38)
[<c01efa80>] (SyS_msgrcv+0x0/0x38) from [<c001a180>] (ret_fast_syscall+0x0/0x48)
tPlay0Cb2       R running      0   297    204 0x00000001

Signed-off-by: Yogesh Gaur <yn.gaur@...sung.com>
Signed-off-by: Manjeet Pawar <manjeet.p@...sung.com>
Reviewed-by : Ajeet Yadav <ajeet.y@...sung.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Tejun Heo <tj@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 ipc/msg.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff -puN ipc/msg.c~msgrcv-use-freezable-blocking-call ipc/msg.c
--- a/ipc/msg.c~msgrcv-use-freezable-blocking-call
+++ a/ipc/msg.c
@@ -37,6 +37,7 @@
 #include <linux/rwsem.h>
 #include <linux/nsproxy.h>
 #include <linux/ipc_namespace.h>
+#include <linux/freezer.h>
 
 #include <asm/current.h>
 #include <linux/uaccess.h>
@@ -915,7 +916,7 @@ long do_msgrcv(int msqid, void __user *b
 
 		ipc_unlock_object(&msq->q_perm);
 		rcu_read_unlock();
-		schedule();
+		freezable_schedule();
 
 		/* Lockless receive, part 1:
 		 * Disable preemption.  We don't hold a reference to the queue
_

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