From 3872c48b14259d8c0a00c9fff06a4a4123f7f4eb Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sat, 31 Mar 2012 12:45:43 +0200 Subject: tick: Document TICK_ONESHOT config option This option has been selected from arch code as it was assumed that it's necessary to support oneshot mode clockevent devices. But it's just a core internal helper to compile tick-oneshot.c if NOHZ or HIG_RES_TIMERS are selected. Reported-by: Russell King Signed-off-by: Thomas Gleixner --- kernel/time/Kconfig | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/time') diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 2cf9cc7aa10..a20dc8a3c94 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -1,6 +1,10 @@ # # Timer subsystem related configuration options # + +# Core internal switch. Selected by NO_HZ / HIGH_RES_TIMERS. This is +# only related to the tick functionality. Oneshot clockevent devices +# are supported independ of this. config TICK_ONESHOT bool -- cgit v1.2.3 From 6f103929f8979d2638e58d7f7fda0beefcb8ee7e Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Tue, 27 Mar 2012 15:09:37 -0400 Subject: nohz: Fix stale jiffies update in tick_nohz_restart() Fix tick_nohz_restart() to not use a stale ktime_t "now" value when calling tick_do_update_jiffies64(now). If we reach this point in the loop it means that we crossed a tick boundary since we grabbed the "now" timestamp, so at this point "now" refers to a time in the old jiffy, so using the old value for "now" is incorrect, and is likely to give us a stale jiffies value. In particular, the first time through the loop the tick_do_update_jiffies64(now) call is always a no-op, since the caller, tick_nohz_restart_sched_tick(), will have already called tick_do_update_jiffies64(now) with that "now" value. Note that tick_nohz_stop_sched_tick() already uses the correct approach: when we notice we cross a jiffy boundary, grab a new timestamp with ktime_get(), and *then* update jiffies. Signed-off-by: Neal Cardwell Cc: Ben Segall Cc: Ingo Molnar Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1332875377-23014-1-git-send-email-ncardwell@google.com Signed-off-by: Thomas Gleixner --- kernel/time/tick-sched.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/time') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 3526038f283..6a3a5b9ff56 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -534,9 +534,9 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) hrtimer_get_expires(&ts->sched_timer), 0)) break; } - /* Update jiffies and reread time */ - tick_do_update_jiffies64(now); + /* Reread time and update jiffies */ now = ktime_get(); + tick_do_update_jiffies64(now); } } -- cgit v1.2.3 From fa4da365bc7772c2cd6d5405bdf151612455f957 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Mon, 9 Apr 2012 15:41:44 -0700 Subject: clockevents: tTack broadcast device mode change in tick_broadcast_switch_to_oneshot() 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 --- kernel/time/tick-broadcast.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'kernel/time') diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index e883f57a3cd..bf57abdc7bd 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -575,10 +575,12 @@ void tick_broadcast_switch_to_oneshot(void) unsigned long flags; raw_spin_lock_irqsave(&tick_broadcast_lock, flags); + + tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT; + if (cpumask_empty(tick_get_broadcast_mask())) goto end; - tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT; bc = tick_broadcast_device.evtdev; if (bc) tick_broadcast_setup_oneshot(bc); -- cgit v1.2.3