[0/4] fanotify: Make wait for permission event response interruptible

Message

Jan Kara Jan. 8, 2019, 4:46 p.m. UTC

Hello,

When waiting for response to fanotify permission events, we currently use
uninterruptible waits. That makes code simple however it can cause lots of
processes to end up in uninterruptible sleep with hard reboot being the only
alternative in case fanotify listener process stops responding (e.g. due to a
bug in its implementation) - reported e.g. in [1]. Uninterruptible sleep also
makes system hibernation fail if the listener gets frozen before the process
generating fanotify permission event (as reported e.g. here [2]).

This patch set modifies fanotify so that it will use interruptible wait when
waiting for fanotify permission event response. Patches are based on current
Linus' tree for the ease of testing (I plan to rebase them on top of Amir's
pending changes later). I have also create LTP test which stresses handling of
permission events while sending processes signals to test the new code - I'll
send that separately later. Review, comments, and testing are welcome.

[1] https://lore.kernel.org/lkml/153474898224.6806.12518115530793064797.stgit@buzz/
[2] https://lore.kernel.org/lkml/[e-mail]/

								Honza

Comments

Jan Kara Jan. 8, 2019, 4:53 p.m. UTC | #1

On Tue 08-01-19 17:46:07, Jan Kara wrote:
> Hello,
> 
> When waiting for response to fanotify permission events, we currently use
> uninterruptible waits. That makes code simple however it can cause lots of
> processes to end up in uninterruptible sleep with hard reboot being the only
> alternative in case fanotify listener process stops responding (e.g. due to a
> bug in its implementation) - reported e.g. in [1]. Uninterruptible sleep also
> makes system hibernation fail if the listener gets frozen before the process
> generating fanotify permission event (as reported e.g. here [2]).
> 
> This patch set modifies fanotify so that it will use interruptible wait when
> waiting for fanotify permission event response. Patches are based on current
> Linus' tree for the ease of testing (I plan to rebase them on top of Amir's
> pending changes later). I have also create LTP test which stresses handling of
> permission events while sending processes signals to test the new code - I'll
> send that separately later. Review, comments, and testing are welcome.
> 
> [1] https://lore.kernel.org/lkml/153474898224.6806.12518115530793064797.stgit@buzz/
> [2] https://lore.kernel.org/lkml/[e-mail]/
> 

Patch adding LTP test I have created for excercising new code is attached.

								Honza