Ingo Molnar wrote:
> Subject: sched: make cpu_clock() not use the rq clock
>
This subject doesn't make much sense to me. All this patch does is get
the rq's current time under irq_disable rather than spinlock, right?
J
> From: Ingo Molnar <[email protected]>
>
> it is enough to disable interrupts to get the precise rq-clock
> of the local CPU.
>
> this also solves an NMI watchdog regression: the NMI watchdog
> calls touch_softlockup_watchdog(), which might deadlock on
> rq->lock if the NMI hits an rq-locked critical section.
>
> Signed-off-by: Ingo Molnar <[email protected]>
> ---
> kernel/sched.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> Index: linux-rt-rebase.q/kernel/sched.c
> ===================================================================
> --- linux-rt-rebase.q.orig/kernel/sched.c
> +++ linux-rt-rebase.q/kernel/sched.c
> @@ -446,13 +446,12 @@ static inline unsigned long long rq_cloc
> */
> unsigned long long cpu_clock(int cpu)
> {
> - struct rq *rq = cpu_rq(cpu);
> unsigned long long now;
> unsigned long flags;
>
> - spin_lock_irqsave(&rq->lock, flags);
> - now = rq_clock(rq);
> - spin_unlock_irqrestore(&rq->lock, flags);
> + local_irq_save(flags);
> + now = rq_clock(cpu_rq(cpu));
> + local_irq_restore(flags);
>
> return now;
> }
> -
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