Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" | Date | Thu, 3 Nov 2011 00:11:23 +0100 |
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On Wednesday, November 02, 2011, Oleg Nesterov wrote: > Hi, > > On 11/01, Tejun Heo wrote: > > > > For now, let's go with the count/dont_count. Can you please write up > > a patch for that? Jeff, does this seem okay to you? > > OK, will do in a minute. On top of > "[PATCH pm] freezer: fix wait_event_freezable/__thaw_task races" > you sent. (btw, thanks, I forgout about it ;) > > Rafael, could you remind why freezer_do_not_count/freezer_count check > ->mm != NULL ?
You're asking difficult questions. ;-)
The intention was to prevent PF_FREEZER_SKIP from having any effect on kernel threads, IIRC. Anyway, there are only two legitimate users of it (vfork and apm_ioctl) and in both cases the task in question is user space.
> The comment says "However, we don't want kernel threads to be frozen", > but it is not clear anyway. A kernel thread simply shouldn't use this > interface if it doesn't want to freeze. > > And in any case, PF_KTHREAD looks better if we really need to filter > out the kernel threads.
PF_FREEZER_SKIP was introduced specifically with vfork in mind and I'm not sure if it's a good idea to re-use it for something else (at least not for something entirely obvious).
Thanks, Rafael
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