On Fri, Jan 9, 2015 at 3:05 AM, Michal Hocko <mhocko@xxxxxxx> wrote:
> /**
> * freeze_processes - Signal user space processes to enter the refrigerator.
> * The current thread will not be frozen. The same process that calls
> @@ -142,7 +118,6 @@ static bool check_frozen_processes(void)
> int freeze_processes(void)
> {
> int error;
> - int oom_kills_saved;
>
> error = __usermodehelper_disable(UMH_FREEZING);
> if (error)
> @@ -157,29 +132,22 @@ int freeze_processes(void)
> pm_wakeup_clear();
> pr_info("Freezing user space processes ... ");
> pm_freezing = true;
> - oom_kills_saved = oom_kills_count();
> error = try_to_freeze_tasks(true);
> if (!error) {
> __usermodehelper_set_disable_depth(UMH_DISABLED);
> - oom_killer_disable();
> -
> - /*
> - * There might have been an OOM kill while we were
> - * freezing tasks and the killed task might be still
> - * on the way out so we have to double check for race.
> - */
> - if (oom_kills_count() != oom_kills_saved &&
> - !check_frozen_processes()) {
> - __usermodehelper_set_disable_depth(UMH_ENABLED);
> - pr_cont("OOM in progress.");
> - error = -EBUSY;
> - } else {
> - pr_cont("done.");
> - }
> + pr_cont("done.");
> }
> pr_cont("\n");
> BUG_ON(in_atomic());
>
> + /*
> + * Now that the whole userspace is frozen we need to disbale
disable
> + * the OOM killer to disallow any further interference with
> + * killable tasks.
> + */
> + if (!error && !oom_killer_disable())
> + error = -EBUSY;
> +
[...]
> void unmark_oom_victim(void)
> {
> - clear_thread_flag(TIF_MEMDIE);
> + if (!test_and_clear_thread_flag(TIF_MEMDIE))
> + return;
> +
> + down_read(&oom_sem);
> + /*
> + * There is no need to signal the lasst oom_victim if there
last
> + * is nobody who cares.
> + */
> + if (!atomic_dec_return(&oom_victims) && oom_killer_disabled)
> + wake_up_all(&oom_victims_wait);
> + up_read(&oom_sem);
> +}
[...]
> /*
> * The pagefault handler calls here because it is out of memory, so kill a
> * memory-hogging task. If any populated zone has ZONE_OOM_LOCKED set, a
> @@ -727,12 +806,25 @@ void pagefault_out_of_memory(void)
> {
> struct zonelist *zonelist;
>
> + down_read(&oom_sem);
> if (mem_cgroup_oom_synchronize(true))
> - return;
> + goto unlock;
>
> zonelist = node_zonelist(first_memory_node, GFP_KERNEL);
> if (oom_zonelist_trylock(zonelist, GFP_KERNEL)) {
> - out_of_memory(NULL, 0, 0, NULL, false);
> + if (!oom_killer_disabled)
> + __out_of_memory(NULL, 0, 0, NULL, false);
> + else
> + /*
> + * There shouldn't be any user tasks runable while the
runnable
> + * OOM killer is disabled so the current task has to
> + * be a racing OOM victim for which oom_killer_disable()
> + * is waiting for.
> + */
> + WARN_ON(test_thread_flag(TIF_MEMDIE));
> +
> oom_zonelist_unlock(zonelist, GFP_KERNEL);
> }
> +unlock:
> + up_read(&oom_sem);
> }
Thanks!
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