lkml.org 
[lkml]   [2012]   [Jun]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 5/9] blackfin: A couple of task->mm handling fixes
Date
On Monday 23 April 2012 03:09:01 Anton Vorontsov wrote:
> 1. Working with task->mm w/o getting mm or grabing the task lock is
> dangerous as ->mm might disappear (exit_mm() assigns NULL under
> task_lock(), so tasklist lock is not enough).

that isn't a problem for this code as it specifically checks if it's in an
atomic section. if it is, then task->mm can't go away on us.

> We can't use get_task_mm()/mmput() pair as mmput() might sleep,
> so we have to take the task lock while handle its mm.

if we're not in an atomic section, then sleeping is fine.

> 2. Checking for process->mm is not enough because process' main
> thread may exit or detach its mm via use_mm(), but other threads
> may still have a valid mm.

i don't think it matters for this code (per the reasons above).

> To catch this we use find_lock_task_mm(), which walks up all
> threads and returns an appropriate task (with task lock held).

certainly fine for the non-atomic code path. i guess we'll notice in crashes
if it causes a problem in atomic code paths as well.
-mike
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2012-06-01 07:21    [W:0.138 / U:0.152 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site