On Fri, Jul 29, 2011 at 7:28 AM, Ben Blum <bblum@xxxxxxxxxxxxxx> wrote: > Fix unstable tasklist locking in cgroup_attach_proc. > > From: Ben Blum <bblum@xxxxxxxxxxxxxx> > > According to this thread - https://lkml.org/lkml/2011/7/27/243 - RCU is > not sufficient to guarantee the tasklist is stable w.r.t. de_thread and > exit. Taking tasklist_lock for reading, instead of rcu_read_lock, > ensures proper exclusion. > > Signed-off-by: Ben Blum <bblum@xxxxxxxxxxxxxx> Acked-by: Paul Menage <menage@xxxxxxxxxx> Thanks, Paul > --- > kernel/cgroup.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff a/kernel/cgroup.c b/kernel/cgroup.c > --- a/kernel/cgroup.c 2011-07-21 19:17:23.000000000 -0700 > +++ b/kernel/cgroup.c 2011-07-29 06:17:47.000000000 -0700 > @@ -2024,7 +2024,7 @@ > goto out_free_group_list; > > /* prevent changes to the threadgroup list while we take a snapshot. */ > - rcu_read_lock(); > + read_lock(&tasklist_lock); > if (!thread_group_leader(leader)) { > /* > * a race with de_thread from another thread's exec() may strip > @@ -2033,7 +2033,7 @@ > * throw this task away and try again (from cgroup_procs_write); > * this is "double-double-toil-and-trouble-check locking". > */ > - rcu_read_unlock(); > + read_unlock(&tasklist_lock); > retval = -EAGAIN; > goto out_free_group_list; > } > @@ -2054,7 +2054,7 @@ > } while_each_thread(leader, tsk); > /* remember the number of threads in the array for later. */ > group_size = i; > - rcu_read_unlock(); > + read_unlock(&tasklist_lock); > > /* > * step 1: check that we can legitimately attach to the cgroup. > _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
