Re: [PATCH] sched: Fix lost reschedule in __cond_resched()

[Linus Torvalds]

On Sun, Dec 14, 2014 at 10:04 AM, Frederic Weisbecker
<fweisbec@xxxxxxxxx> wrote:
>
> Such as:

So I like your patch, but quite frankly, can we go one step further?

Look at the callers of __schedule().

EVERY SINGLE ONE now has that loop around it that goes along the lines of

   do {
      .. disable preemption somehow ..
      __schedule();
      ...enable preemption without scheduling ..
   } while (need_resced());

except for one - the regular "schedule()" function.

Furthermore, look inside __schedule() itself: it has the same loop,
except with a count of one.

So I would suggest going the extra mile, and
 - remove the loop from __schedule() itself
 - add the same loop as everywhere else to "schedule()"

IOW, just make this "you have to loop and disable preemption" thing be
a rule that __schedule() can depend on.

                 Linus
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