user/sven/linux.git/kernel/time/tick-broadcast.c, branch v3.6.3

tick: Fix the spurious broadcast timer ticks after resume

2012-04-19T19:27:50Z

During resume, tick_resume_broadcast() programs the broadcast timer in oneshot mode unconditionally. On the platforms where broadcast timer is not really required, this will generate spurious broadcast timer ticks upon resume. For example, on the always running apic timer platforms with HPET, I see spurious hpet tick once every ~5minutes (which is the 32-bit hpet counter wraparound time). Similar to boot time, during resume make the oneshot mode setting of the broadcast clock event device conditional on the state of active broadcast users. Signed-off-by: Suresh Siddha Tested-by: Santosh Shilimkar Tested-by: svenjoac@gmx.de Cc: torvalds@linux-foundation.org Cc: rjw@sisk.pl Link: http://lkml.kernel.org/r/1334802459.28674.209.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Thomas Gleixner

tick: Ensure that the broadcast device is initialized

2012-04-19T19:27:35Z

Santosh found another trap when we avoid to initialize the broadcast device in the switch_to_oneshot code. The broadcast device might be still in SHUTDOWN state when we actually need to use it. That obviously breaks, as set_next_event() is called on a shutdown device. This did not break on x86, but Suresh analyzed it: From the review, most likely on Sven's system we are force enabling the hpet using the pci quirk's method very late. And in this case, hpet_clockevent (which will be global_clock_event) handler can be null, specifically as this platform might not be using deeper c-states and using the reliable APIC timer. Prior to commit 'fa4da365bc7772c', that handler will be set to 'tick_handle_oneshot_broadcast' when we switch the broadcast timer to oneshot mode, even though we don't use it. Post commit 'fa4da365bc7772c', we stopped switching the broadcast mode to oneshot as this is not really needed and his platform's global_clock_event's handler will remain null. While on my SNB laptop, same is set to 'clockevents_handle_noop' because hpet gets enabled very early. (noop handler on my platform set when the early enabled hpet timer gets replaced by the lapic timer). But the commit 'fa4da365bc7772c' tracked the broadcast timer mode in the SW as oneshot, even though it didn't touch the HW timer. During resume however, tick_resume_broadcast() saw the SW broadcast mode as oneshot and actually programmed the broadcast device also into oneshot mode. So this triggered the null pointer de-reference after the hpet wraps around and depending on what the hpet counter is set to. On the normal platforms where hpet gets enabled early we should be seeing a spurious interrupt (in my SNB laptop I see one spurious interrupt after around 5 minutes ;) which is 32-bit hpet counter wraparound time), but that's a separate issue. Enforce the mode setting when trying to set an event. Reported-and-tested-by: Santosh Shilimkar Signed-off-by: Thomas Gleixner Acked-by: Suresh Siddha Cc: torvalds@linux-foundation.org Cc: svenjoac@gmx.de Cc: rjw@sisk.pl Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1204181723350.2542@ionos

tick: Fix oneshot broadcast setup really

2012-04-18T12:00:56Z

Sven Joachim reported, that suspend/resume on rc3 trips over a NULL pointer dereference. Linus spotted the clockevent handler being NULL. commit fa4da365b(clockevents: tTack broadcast device mode change in tick_broadcast_switch_to_oneshot()) tried to fix a problem with the broadcast device setup, which was introduced in commit 77b0d60c5( clockevents: Leave the broadcast device in shutdown mode when not needed). The initial commit avoided to set up the broadcast device when no broadcast request bits were set, but that left the broadcast device disfunctional. In consequence deep idle states which need the broadcast device were not woken up. commit fa4da365b tried to fix that by initializing the state of the broadcast facility, but that missed the fact, that nothing initializes the event handler and some other state of the underlying clock event device. The fix is to revert both commits and make only the mode setting of the clock event device conditional on the state of active broadcast users. That initializes everything except the low level device mode, but this happens when the broadcast functionality is invoked by deep idle. Reported-and-tested-by: Sven Joachim Signed-off-by: Thomas Gleixner Cc: Rafael J. Wysocki Cc: Linus Torvalds Cc: Suresh Siddha Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1204181205540.2542@ionos

clockevents: tTack broadcast device mode change in tick_broadcast_switch_to_oneshot()

2012-04-10T09:42:07Z

In the commit 77b0d60c5adf39c74039e2142a1d3cd1e4d53799, "clockevents: Leave the broadcast device in shutdown mode when not needed", we were bailing out too quickly in tick_broadcast_switch_to_oneshot(), with out tracking the broadcast device mode change to 'TICKDEV_MODE_ONESHOT'. This breaks the platforms which need broadcast device oneshot services during deep idle states. tick_broadcast_oneshot_control() thinks that it is in periodic mode and fails to take proper decisions based on the CLOCK_EVT_NOTIFY_BROADCAST_[ENTER, EXIT] notifications during deep idle entry/exit. Fix this by tracking the broadcast device mode as 'TICKDEV_MODE_ONESHOT', before leaving the broadcast HW device in shutdown mode if there are no active requests for the moment. Reported-and-tested-by: Santosh Shilimkar Signed-off-by: Suresh Siddha Cc: johnstul@us.ibm.com Link: http://lkml.kernel.org/r/1334011304.12400.81.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Thomas Gleixner

clockevents: Leave the broadcast device in shutdown mode when not needed

2012-02-15T14:23:09Z

Platforms with Always Running APIC Timer doesn't use the broadcast timer but the kernel is leaving the broadcast timer (HPET in this case) in oneshot mode. On these platforms, before the switch to oneshot mode, broadcast device is actually in shutdown mode. Code checks for empty tick_broadcast_mask and avoids going into the periodic mode. During switch to oneshot mode, add the same tick_broadcast_mask checks in the tick_broadcast_switch_to_oneshot() and avoid the broadcast device going into the oneshot mode. Signed-off-by: Suresh Siddha Cc: john stultz Cc: venki@google.com Link: http://lkml.kernel.org/r/1320452301.15071.16.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Thomas Gleixner

tick-broadcast: Stop active broadcast device when replacing it

2011-12-02T15:06:54Z

When a better rated broadcast device is installed, then the current active device is not disabled, which results in two running broadcast devices. Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org

clockevents: Make minimum delay adjustments configurable

2011-09-08T09:10:56Z

The automatic increase of the min_delta_ns of a clockevents device should be done in the clockevents code as the minimum delay is an attribute of the clockevents device. In addition not all architectures want the automatic adjustment, on a massively virtualized system it can happen that the programming of a clock event fails several times in a row because the virtual cpu has been rescheduled quickly enough. In that case the minimum delay will erroneously be increased with no way back. The new config symbol GENERIC_CLOCKEVENTS_MIN_ADJUST is used to enable the automatic adjustment. The config option is selected only for x86. Signed-off-by: Martin Schwidefsky Cc: john stultz Link: http://lkml.kernel.org/r/20110823133142.494157493@de.ibm.com Signed-off-by: Thomas Gleixner

Merge branch 'timers/urgent' into timers/core

2011-05-20T18:08:05Z

Reason: Get upstream fixes and kfree_rcu which is necessary for a follow up patch. Signed-off-by: Thomas Gleixner

tick: Clear broadcast active bit when switching to oneshot

2011-05-16T21:35:41Z

The first cpu which switches from periodic to oneshot mode switches also the broadcast device into oneshot mode. The broadcast device serves as a backup for per cpu timers which stop in deeper C-states. To avoid starvation of the cpus which might be in idle and depend on broadcast mode it marks the other cpus as broadcast active and sets the brodcast expiry value of those cpus to the next tick. The oneshot mode broadcast bit for the other cpus is sticky and gets only cleared when those cpus exit idle. If a cpu was not idle while the bit got set in consequence the bit prevents that the broadcast device is armed on behalf of that cpu when it enters idle for the first time after it switched to oneshot mode. In most cases that goes unnoticed as one of the other cpus has usually a timer pending which keeps the broadcast device armed with a short timeout. Now if the only cpu which has a short timer active has the bit set then the broadcast device will not be armed on behalf of that cpu and will fire way after the expected timer expiry. In the case of Christians bug report it took ~145 seconds which is about half of the wrap around time of HPET (the limit for that device) due to the fact that all other cpus had no timers armed which expired before the 145 seconds timeframe. The solution is simply to clear the broadcast active bit unconditionally when a cpu switches to oneshot mode after the first cpu switched the broadcast device over. It's not idle at that point otherwise it would not be executing that code. [ I fundamentally hate that broadcast crap. Why the heck thought some folks that when going into deep idle it's a brilliant concept to switch off the last device which brings the cpu back from that state? ] Thanks to Christian for providing all the valuable debug information! Reported-and-tested-by: Christian Hoffmann Cc: John Stultz Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1105161105170.3078%40ionos%3E Cc: stable@kernel.org Signed-off-by: Thomas Gleixner

clockevents: Move C3 stop test outside lock

2011-05-05T15:32:13Z

Avoid taking broadcast_lock in the idle path for systems where the timer doesn't stop in C3. [ tglx: Removed the stale label and added comment ] Signed-off-by: Andi Kleen Cc: Dave Kleikamp Cc: Chris Mason Cc: Peter Zijlstra Cc: Tim Chen Cc: lenb@kernel.org Cc: paulmck@us.ibm.com Link: http://lkml.kernel.org/r/%3C20110504234806.GF2925%40one.firstfloor.org%3E Signed-off-by: Thomas Gleixner