Messages in this thread | | | Date | Tue, 29 Sep 2015 07:55:49 -0400 | Subject | Re: [RFC][PATCH v2 12/11] sched: Add preempt_count invariant check | From | Linus Torvalds <> |
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On Tue, Sep 29, 2015 at 6:56 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > + * Initial preempt_count value; reflects the preempt_count schedule invariant > + * which states that during schedule preempt_count() == 2.
Is this actually *true*?
preempt_count() is two only if preemption is enabled. But spinlocks do not actually update the preemption count if there is no preemption, so these kinds of checks and comments that aren't even inside #ifdef CONFIG_PREEMPT seem to be actively misleading.
I do believe that the preempt count is stable - but the actual value would seem to depend on config options.
Linus
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