Re: [PATCH 03/10] threadgroup: extend threadgroup_lock() to coverexit and exec

[KAMEZAWA Hiroyuki]

On Tue,  1 Nov 2011 16:46:26 -0700
Tejun Heo <tj@xxxxxxxxxx> wrote:

> threadgroup_lock() protected only protected against new addition to
> the threadgroup, which was inherently somewhat incomplete and
> problematic for its only user cgroup.  On-going migration could race
> against exec and exit leading to interesting problems - the symmetry
> between various attach methods, task exiting during method execution,
> ->exit() racing against attach methods, migrating task switching basic
> properties during exec and so on.
> 
> This patch extends threadgroup_lock() such that it protects against
> all three threadgroup altering operations - fork, exit and exec.  For
> exit, threadgroup_change_begin/end() calls are added to exit path.
> For exec, threadgroup_[un]lock() are updated to also grab and release
> cred_guard_mutex.
> 
> With this change, threadgroup_lock() guarantees that the target
> threadgroup will remain stable - no new task will be added, no new
> PF_EXITING will be set and exec won't happen.
> 
> The next patch will update cgroup so that it can take full advantage
> of this change.
> 
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul Menage <paul@xxxxxxxxxxxxxx>
> Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>


Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

--
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/