[PATCH 5/9] blackfin: A couple of task->mm handling fixes
vapier at gentoo.org
Fri Jun 1 14:36:35 EST 2012
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.
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 836 bytes
Desc: This is a digitally signed message part.
More information about the Linuxppc-dev