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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>
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@ -675,9 +675,11 @@ static inline loff_t i_size_read(const struct inode *inode)
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static inline void i_size_write(struct inode *inode, loff_t i_size)
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{
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#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
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preempt_disable();
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write_seqcount_begin(&inode->i_size_seqcount);
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inode->i_size = i_size;
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write_seqcount_end(&inode->i_size_seqcount);
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preempt_enable();
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#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
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preempt_disable();
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inode->i_size = i_size;
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