[3.5.y.z extended stable] Patch "include/linux/fs.h: disable preempt when acquire i_size_seqcount" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Fri Nov 22 11:35:10 UTC 2013
This is a note to let you know that I have just added a patch titled
include/linux/fs.h: disable preempt when acquire i_size_seqcount
to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From 2127ef25e5778f4878085862ce4b8fc9815e24d5 Mon Sep 17 00:00:00 2001
From: Fan Du <fan.du at windriver.com>
Date: Tue, 30 Apr 2013 15:27:27 -0700
Subject: include/linux/fs.h: disable preempt when acquire i_size_seqcount
write lock
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 at windriver.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Zhao Hongjiang <zhaohongjiang at huawei.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
include/linux/fs.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 17fd887..65b8b69 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -925,9 +925,11 @@ static inline loff_t i_size_read(const struct inode *inode)
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;
--
1.8.3.2
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