3.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Fan Du <fan...@windriver.com> 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...@windriver.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Cc: Zhao Hongjiang <zhaohongji...@huawei.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/