Re: [patch for-3.7] mm, mempolicy: fix printing stack contents innuma_maps

[David Rientjes]

On Tue, 16 Oct 2012, KOSAKI Motohiro wrote:

> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 0b78fb9..d04a8a5 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -1536,9 +1536,8 @@ asmlinkage long compat_sys_mbind(compat_ulong_t start, compat_ulong_t len,
> >   *
> >   * Returns effective policy for a VMA at specified address.
> >   * Falls back to @task or system default policy, as necessary.
> > - * Current or other task's task mempolicy and non-shared vma policies
> > - * are protected by the task's mmap_sem, which must be held for read by
> > - * the caller.
> > + * Current or other task's task mempolicy and non-shared vma policies must be
> > + * protected by task_lock(task) by the caller.
> 
> This is not correct. mmap_sem is needed for protecting vma. task_lock()
> is needed to close vs exit race only when task != current. In other word,
> caller must held both mmap_sem and task_lock if task != current.
> 

The comment is specifically addressing non-shared vma policies, you do not 
need to hold mmap_sem to access another thread's mempolicy.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/