Re: INFO: task hung in blk_queue_enter

Alan Jenkins
2018-05-16T17:33:36Z

> jbd2/sda1-8(PID=2271) is stuck waiting for journal commit operation.
> I don't know how this thread is involved to this problem.

It feels like it should be a necessary link in the chain. This is the
filesystem underneath the loop device. If that hangs, we would expect
the loop device to hang, but not vice versa.

AIUI, you couldn't reproduce this hang on your own machine.

Don't you think, your fuzzer has just found a nice exploit for reiserfs?

Alan

(It's interesting that you found this hang just after we fixed
block_queue_enter() to wait in D state instead of S state.[1]  I don't
know syszkaller, so I assume from this it only flagged this case up
because of the hung task warning. I.e. syzkaller didn't have its own
watchdog that would have failed the test anyway.

[1] the commit that caused you to CC me. "block: do not use
interruptible wait anywhere"

https://github.com/torvalds/linux/commit/1dc3039bc87ae7d19a990c3ee71cfd8a9068f428

)