On 10/27, Ben Hutchings wrote: > > On Fri, 2012-10-26 at 19:46 +0200, Oleg Nesterov wrote: > > try_to_freeze_tasks() and cgroup_freezer rely on scheduler locks > > to ensure that a task doing STOPPED/TRACED -> RUNNING transition > > can't escape freezing. This mostly works, but ptrace_stop() does > > not necessarily call schedule(), it can change task->state back to > > RUNNING and check freezing() without any lock/barrier in between. > > > > We could add the necessary barrier, but this patch changes > > ptrace_stop() and do_signal_stop() to use freezable_schedule(). > > This fixes the race, freezer_count() and freezer_should_skip() > > carefully avoid the race. > > > > And this simplifies the code, try_to_freeze_tasks/update_if_frozen > > no longer need to use task_is_stopped_or_traced() checks with the > > non trivial assumptions. We can rely on the mechanism which was > > specially designed to mark the sleeping task as "frozen enough". > > > > v2: As Tejun pointed out, we can also change get_signal_to_deliver() > > and move try_to_freeze() up before 'relock' label. > > > > Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> > [...] > > This is not the correct way to submit a change to stable. Please see > Documentation/stable_kernel_rules.txt Sorry for confusion, it is not for stable@, it was cc'ed by mistake. Oleg. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
