Re: !PageLocked from shmem charge path hits VM_BUG_ON with 4.4-rc4

From: Michal Hocko
Date: Mon Dec 14 2015 - 07:06:29 EST

On Mon 14-12-15 12:03:20, Michal Hocko wrote:
> JFYI: Andrey Ryabinin has noticed that this might be related to
> and indeed if somebody with pending signals would do wait_on_page_locked
> then it could race AFAIU.

No, a simple lock_page would fail to lock the page (thanks Andrey for
the clarification in the parallel email thread). I have missed that
__lock_page uses bit_wait_io and that would return EINTR when using
signal_pending. The fix has changed that to singnal_pending_state so
this will not happen anymore. I think the mystery is solved...

Michal Hocko
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