diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2012-10-26 19:46:06 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2012-10-26 14:27:49 -0700 |
| commit | 5d8f72b55c275677865de670fa147ed318191d81 (patch) | |
| tree | 58f4f571440f412861a232ed0c5753771e5a6e58 /kernel/cgroup_freezer.c | |
| parent | ead5c473712eb26db792b18a4dc98fdb312883fe (diff) | |
freezer: change ptrace_stop/do_signal_stop to use freezable_schedule()
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@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup_freezer.c')
| -rw-r--r-- | kernel/cgroup_freezer.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 8a92b0e5209..bedefd9a22d 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -198,8 +198,7 @@ static void update_if_frozen(struct cgroup *cgroup, struct freezer *freezer) * completion. Consider it frozen in addition to * the usual frozen condition. */ - if (!frozen(task) && !task_is_stopped_or_traced(task) && - !freezer_should_skip(task)) + if (!frozen(task) && !freezer_should_skip(task)) goto notyet; } } |