Re: INFO: task hung in __sb_start_write

[Dmitry Vyukov]

On Mon, Jun 11, 2018 at 9:30 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Sun, Jun 10, 2018 at 11:47:56PM +0900, Tetsuo Handa wrote:
>
>> This looks quite strange that nobody is holding percpu_rw_semaphore for
>> write but everybody is stuck trying to hold it for read. (Since there
>> is no "X locks held by ..." line without followup "#0:" line, there is
>> no possibility that somebody is in TASK_RUNNING state while holding
>> percpu_rw_semaphore for write.)
>>
>> I feel that either API has a bug or API usage is wrong.
>> Any idea for debugging this?
>
> Look at percpu_rwsem_release() and usage. The whole fs freezer thing is
> magic.

Do you mean that we froze fs? We tried to never-ever issue
ioctl(FIFREEZE) during fuzzing. Are there other ways to do this?