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authorFan Du <fan.du@windriver.com>2013-04-30 15:27:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-30 17:04:03 -0700
commit74e3d1e17b2e11d175970b85acd44f5927000ba2 (patch)
tree1adaccdd30702c8c151dfb97b13aaf241e092849 /include/linux/fs.h
parent3440a1ca99707f093e9568ba9762764d3162dd8f (diff)
downloadlinaro-lsk-74e3d1e17b2e11d175970b85acd44f5927000ba2.tar.gz
include/linux/fs.h: disable preempt when acquire i_size_seqcount write lock
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@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/fs.h')
-rw-r--r--include/linux/fs.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2c28271ab9d..17d8b159621 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -675,9 +675,11 @@ 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;