This is a note to let you know that I've just added the patch titled
include/linux/fs.h: disable preempt when acquire i_size_seqcount write lock
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
include-linux-fs.h-disable-preempt-when-acquire-i_size_seqcount-write-lock.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 74e3d1e17b2e11d175970b85acd44f5927000ba2 Mon Sep 17 00:00:00 2001
From: Fan Du <fan.du@xxxxxxxxxxxxx>
Date: Tue, 30 Apr 2013 15:27:27 -0700
Subject: include/linux/fs.h: disable preempt when acquire i_size_seqcount write lock
From: Fan Du <fan.du@xxxxxxxxxxxxx>
commit 74e3d1e17b2e11d175970b85acd44f5927000ba2 upstream.
Two rt tasks bind to one CPU core.
The higher priority rt task A preempts a lower priority rt task B which
has already taken the write seq lock, and then the higher priority rt
task A try to acquire read seq lock, it's doomed to lockup.
rt task A with lower priority: call write
i_size_write rt task B with higher priority: call sync, and preempt task A
write_seqcount_begin(&inode->i_size_seqcount); i_size_read
inode->i_size = i_size; read_seqcount_begin <-- lockup here...
So disable preempt when acquiring every i_size_seqcount *write* lock will
cure the problem.
Signed-off-by: Fan Du <fan.du@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Zhao Hongjiang <zhaohongjiang@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/fs.h | 2 ++
1 file changed, 2 insertions(+)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -915,9 +915,11 @@ static inline loff_t i_size_read(const s
static inline void i_size_write(struct inode *inode, loff_t i_size)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+ preempt_disable();
write_seqcount_begin(&inode->i_size_seqcount);
inode->i_size = i_size;
write_seqcount_end(&inode->i_size_seqcount);
+ preempt_enable();
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
preempt_disable();
inode->i_size = i_size;
Patches currently in stable-queue which might be from fan.du@xxxxxxxxxxxxx are
queue-3.4/include-linux-fs.h-disable-preempt-when-acquire-i_size_seqcount-write-lock.patch
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