On Thu, Jul 18, 2013 at 03:57:26PM +0800, Zhouping Liu wrote:
> On 07/18/2013 01:00 PM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> > The patch below does not apply to the 3.10-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@xxxxxxxxxxxxxxx>.
>
> Hi Greg,
>
> Its prerequisite patch is:
> 7c4c3a0f18b hrtimers: Support resuming with two or more CPUs online (but
> stopped)
> how about also back-port this patch?
I could do that, but from reading the changelog comments below, is this
patch really needed for 3.10-stable? 3.11 seems to make sense, as some
other code was using this api and causing problems, but that isn't in
3.10 from what I can tell, right?
So, is it really needed for 3.10?
thanks,
greg k-h
> > ------------------ original commit in Linus's tree ------------------
> >
> > From 5ec2481b7b47a4005bb446d176e5d0257400c77d Mon Sep 17 00:00:00 2001
> > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Date: Fri, 5 Jul 2013 12:09:18 +0200
> > Subject: [PATCH] hrtimers: Move SMP function call to thread context
> >
> > smp_call_function_* must not be called from softirq context.
> >
> > But clock_was_set() which calls on_each_cpu() is called from softirq
> > context to implement a delayed clock_was_set() for the timer interrupt
> > handler. Though that almost never gets invoked. A recent change in the
> > resume code uses the softirq based delayed clock_was_set to support
> > Xens resume mechanism.
> >
> > linux-next contains a new warning which warns if smp_call_function_*
> > is called from softirq context which gets triggered by that Xen
> > change.
> >
> > Fix this by moving the delayed clock_was_set() call to a work context.
> >
> > Reported-and-tested-by: Artem Savkov <artem.savkov@xxxxxxxxx>
> > Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> > Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: H. Peter Anvin <hpa@xxxxxxxxx>,
> > Cc: Konrad Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: John Stultz <john.stultz@xxxxxxxxxx>
> > Cc: xen-devel@xxxxxxxxxxxxx
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> >
> > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
> > index e86827e..b9b9420 100644
> > --- a/kernel/hrtimer.c
> > +++ b/kernel/hrtimer.c
> > @@ -721,17 +721,20 @@ static int hrtimer_switch_to_hres(void)
> > return 1;
> > }
> >
> > +static void clock_was_set_work(struct work_struct *work)
> > +{
> > + clock_was_set();
> > +}
> > +
> > +static DECLARE_WORK(hrtimer_work, clock_was_set_work);
> > +
> > /*
> > - * Called from timekeeping code to reprogramm the hrtimer interrupt
> > - * device. If called from the timer interrupt context we defer it to
> > - * softirq context.
> > + * Called from timekeeping and resume code to reprogramm the hrtimer
> > + * interrupt device on all cpus.
> > */
> > void clock_was_set_delayed(void)
> > {
> > - struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
> > -
> > - cpu_base->clock_was_set = 1;
> > - __raise_softirq_irqoff(HRTIMER_SOFTIRQ);
> > + schedule_work(&hrtimer_work);
> > }
> >
> > #else
> > @@ -775,12 +778,7 @@ void clock_was_set(void)
> > * During resume we might have to reprogram the high resolution timer
> > * interrupt on all online CPUs. However, all other CPUs will be
> > * stopped with IRQs interrupts disabled so the clock_was_set() call
> > - * must be deferred to the softirq.
> > - *
> > - * The one-shot timer has already been programmed to fire immediately
> > - * (see tick_resume_oneshot()) and this interrupt will trigger the
> > - * softirq to run early enough to correctly reprogram the timers on
> > - * all CPUs.
> > + * must be deferred.
> > */
> > void hrtimers_resume(void)
> > {
> > @@ -789,8 +787,10 @@ void hrtimers_resume(void)
> > WARN_ONCE(!irqs_disabled(),
> > KERN_INFO "hrtimers_resume() called with IRQs enabled!");
> >
> > - cpu_base->clock_was_set = 1;
> > - __raise_softirq_irqoff(HRTIMER_SOFTIRQ);
> > + /* Retrigger on the local CPU */
> > + retrigger_next_event(NULL);
> > + /* And schedule a retrigger for all others */
> > + clock_was_set_delayed();
> > }
> >
> > static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
> > @@ -1441,13 +1441,6 @@ void hrtimer_peek_ahead_timers(void)
> >
> > static void run_hrtimer_softirq(struct softirq_action *h)
> > {
> > - struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
> > -
> > - if (cpu_base->clock_was_set) {
> > - cpu_base->clock_was_set = 0;
> > - clock_was_set();
> > - }
> > -
> > hrtimer_peek_ahead_timers();
> > }
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe stable" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>
> --
> To unsubscribe from this list: send the line "unsubscribe stable" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html