* [BUG] fs: possible ABBA deadlocks in do_thaw_all_callback() and freeze_bdev()
@ 2021-12-10 4:03 Jia-Ju Bai
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From: Jia-Ju Bai @ 2021-12-10 4:03 UTC (permalink / raw)
To: viro, andrea, axboe, hch; +Cc: linux-fsdevel, linux-kernel, linux-block
Hello,
My static analysis tool reports several possible ABBA deadlocks in Linux
5.10:
do_thaw_all_callback()
down_write(&sb->s_umount); --> Line 1028 (Lock A)
emergency_thaw_bdev()
thaw_bdev()
mutex_lock(&bdev->bd_fsfreeze_mutex); --> Line 602 (Lock B)
freeze_bdev()
mutex_lock(&bdev->bd_fsfreeze_mutex); --> Line 556 (Lock B)
freeze_super()
down_write(&sb->s_umount); --> Line 1716 (Lock A)
down_write(&sb->s_umount); --> Line 1738 (Lock A)
deactivate_super()
down_write(&s->s_umount); --> Line 365 (Lock A)
When do_thaw_all_callback() and freeze_bdev() are concurrently executed,
the deadlocks can occur.
I am not quite sure whether these possible deadlocks are real and how to
fix them if them are real.
Any feedback would be appreciated, thanks :)
Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Best wishes,
Jia-Ju Bai
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2021-12-10 4:03 [BUG] fs: possible ABBA deadlocks in do_thaw_all_callback() and freeze_bdev() Jia-Ju Bai
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