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Date: Thu, 5 Jan 2012 18:27:29 +0800
From: Feng Tang <feng.tang@...el.com>
To: Tim Gardner <tim.gardner@...onical.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>,
Jonathan Nieder <jrnieder@...il.com>,
Thomas Gleixner <tglx@...utronix.de>, Greg KH <gregkh@...e.de>,
<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
<akpm@...ux-foundation.org>, Alan Cox <alan@...rguk.ukuu.org.uk>,
Phil Miller <mille121@...inois.edu>, <philipl@...rt.org>,
<mjt@....msk.ru>, <gurligebis@...il.com>,
Linux Kernel Mail List <linux-kernel@...r.kernel.org>
Subject: Re: [27/27] clockevents: Set noop handler in
clockevents_exchange_device()
Hi Tim and all,
> From: Tim Gardner <tim.gardner@...onical.com>
> Date: 2011/12/30
> Subject: Re: [27/27] clockevents: Set noop handler in
> clockevents_exchange_device()
> To: Linus Torvalds <torvalds@...ux-foundation.org>
> 抄送： Jonathan Nieder <jrnieder@...il.com>, Thomas Gleixner
> <tglx@...utronix.de>, Greg KH <gregkh@...e.de>,
> linux-kernel@...r.kernel.org, stable@...r.kernel.org,
> akpm@...ux-foundation.org, Alan Cox <alan@...rguk.ukuu.org.uk>, Phil
> Miller <mille121@...inois.edu>
>
>
> On 12/29/2011 06:05 PM, Linus Torvalds wrote:
> >
> > On Thu, Dec 29, 2011 at 4:09 AM, Jonathan Nieder<jrnieder@...il.com> wrote:
> >>
> >>
> >> This is basically the reverse of 7c1e768974 (clockevents: prevent
> >> clockevent event_handler ending up handler_noop, 2008-09-03). The
> >> rationale for the latter still applies.
> >
> >
> > Hmm. You seem to be right. Instead of applying this to stable, it
> > looks like we should revert it from mainline.
> >
> >> People have been reporting
> >> the analagous patch to this one causing hangs on resume in 3.1.y and
> >> 3.2 release candidates:
> >>
> >> - http://thread.gmane.org/gmane.linux.kernel/1233033
> >> - http://thread.gmane.org/gmane.linux.kernel/1233389
> >> - http://thread.gmane.org/gmane.linux.kernel/1233159
> >> - http://thread.gmane.org/gmane.linux.kernel/1227868/focus=1230877
> >>
> >> So please consider reverting it for now.
> >
> >
> > Thomas? It does seem to be broken and there do seem to be regression
> > reports about it.
> >
> > Should I revert it, or do you have alternative fixes?
> >
> > Linus
> > --
>
>
> We (Ubuntu) are seeing this issue as well in both 3.0.13 and 3.2-rc6:
>
> https://lkml.org/lkml/2011/12/24/33
>
> Reverting that single patch alleviates the resume regression.
I had a Dell Studio XPS machine which see the same hang issue. Per my
track, the root cause of the hang should be:
The machine has 8 CPUs and several Hpets, and it use one hpet as its
broadcast tick device, and 5 hpets as per-cpu tick device for CPU 0-4,
3 Lapics as per-cpu tick device for CPU 5-7.
During the resume cycle, for CPU0-4, the per-cpu tick device setup is
a little complex, a lapic will be assigned as the per-cpu tick first,
and then there will be a switch from lapic to hpet, and problem happens
here during the switch:
tick_check_new_device()
->clockevents_exchange_device(): set the noop handler to lapic tick
->tick_setup_device(): pass the lapic's handler(noop handler) to hpet
So after the resume, 5 per-cpu hpet device's handler will be all noop handler
instead of hrtimer_interrupt, which will hang the resuming.
Following is a patch which fix the problem on my side, could you please review
and try?
-------------------------------------------------------------------------
diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index d6733e2..aa93eca 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -101,6 +101,10 @@ struct clock_event_device {
int irq;
const struct cpumask *cpumask;
struct list_head list;
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+ struct tick_device *td;
+#endif
} ____cacheline_aligned;
/*
diff --git a/include/linux/tick.h b/include/linux/tick.h
index b232ccc..7000b26 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -17,6 +17,7 @@ enum tick_device_mode {
struct tick_device {
struct clock_event_device *evtdev;
+ void (*last_event_handler)(struct clock_event_device *);
enum tick_device_mode mode;
};
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 13dfaab..53db16f 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -286,6 +286,15 @@ void clockevents_exchange_device(struct clock_event_device *old,
* released list and do a notify add later.
*/
if (old) {
+ /*
+ * If the old device is the per-cpu tick device, then we
+ * need to record its event handler, so that it could be
+ * passed to the new tick device in tick_setup_device()
+ */
+ if (old->td) {
+ old->td->last_event_handler = old->event_handler;
+ old->td = NULL;
+ }
old->event_handler = clockevents_handle_noop;
clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
list_del(&old->list);
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 119528d..5ec54e9 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -173,12 +173,12 @@ static void tick_setup_device(struct tick_device *td,
*/
td->mode = TICKDEV_MODE_PERIODIC;
} else {
- handler = td->evtdev->event_handler;
+ handler = td->last_event_handler;
next_event = td->evtdev->next_event;
- td->evtdev->event_handler = clockevents_handle_noop;
}
td->evtdev = newdev;
+ newdev->td = td;
/*
* When the device is not per cpu, pin the interrupt to the
>
> rtg
> --
> Tim Gardner tim.gardner@...onical.com
>
> --
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