lkml.org 
[lkml]   [2008]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] poll: allow f_op->poll to sleep, take#6
On Thu, 27 Nov 2008, Tejun Heo wrote:

> f_op->poll is the only vfs operation which is not allowed to sleep. It's
> because poll and select implementation used task state to synchronize
> against wake ups, which doesn't have to be the case anymore as wait/wake
> interface can now use custom wake up functions. The non-sleep restriction
> can be a bit tricky because ->poll is not called from an atomic context
> and the result of accidentally sleeping in ->poll only shows up as
> temporary busy looping when the timing is right or rather wrong.
>
> This patch converts poll/select to use custom wake up function and use
> separate triggered variable to synchronize against wake up events. The
> only added overhead is an extra function call during wake up and
> negligible.
>
> This patch removes the one non-sleep exception from vfs locking rules and
> is beneficial to userland filesystem implementations like FUSE, 9p or
> peculiar fs like spufs as it's very difficult for those to implement
> non-sleeping poll method.

Looks OK to me, although it'd be better if some more folks eye it, in
order to avoid painful mistakes.
Did you test it al all in a live system?


- Davide




\
 
 \ /
  Last update: 2008-11-28 05:39    [W:0.046 / U:2.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site