Messages in this thread | | | From | Kirill Tkhai <> | Subject | Re: [RFC][PATCH 3/7] sched: Allow balance callbacks for check_class_changed() | Date | Wed, 03 Jun 2015 13:42:41 +0300 |
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[resend]
03.06.2015, 10:32, "Peter Zijlstra" <peterz@infradead.org>: > On Tue, Jun 02, 2015 at 07:27:19PM +0300, Kirill Tkhai wrote: >>> + * task_dead_dl() will cancel our timer if we happen to die while >>> + * its still pending. >> task_dead_dl() is called for tasks of deadline class only. So if we do that, >> the timer may be executed after final task's dead. > > Indeed; sleep deprived brain misses the obvious :/
I have an idea, but it require small hrtimer modification. We may use task_struct counters {get,put}_task_struct(), when we're starting or cancelling the timer, and in timer handler. But it require to return back the commit:
commit 61699e13072a89880aa584dcc64c6da465fb2ccc Author: Thomas Gleixner <tglx@linutronix.de> Date: Tue Apr 14 21:09:23 2015 +0000
hrtimer: Remove hrtimer_start() return value
because restart of the timer races with time handler.
Also, it's not clearly for me if it's safe to do the final put_task_struct() from irq context and how it worsens life of RT people.
> I can't seem to come up with anything much better than pulling that > hrtimer_cancel() into finish_task_switch(), however sad that is. > > Something like: > > for_each_class(class) { > if (class->task_dead) > class->task_dead(prev); > } > > Would be nicest, but will slow down the common case. And a callback list > has the downside of having to preallocate entries for every task, > causing mostly pointless memory overhead.
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