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authorThomas Gleixner <tglx@linutronix.de>2008-09-22 18:46:37 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-09-23 11:38:52 +0200
commit6441402b1f173fa38e561d3cee7c01c32e5281ad (patch)
treefd7c81337354f39e44581530d499bcdda06d76c4 /kernel/time/tick-internal.h
parent72d31053f62c4bc464c2783974926969614a8649 (diff)
downloadlinaro-lsk-6441402b1f173fa38e561d3cee7c01c32e5281ad.tar.gz
clockevents: prevent cpu online to interfere with nohz
Impact: rare hang which can be triggered on CPU online. tick_do_timer_cpu keeps track of the CPU which updates jiffies via do_timer. The value -1 is used to signal, that currently no CPU is doing this. There are two cases, where the variable can have this state: boot: necessary for systems where the boot cpu id can be != 0 nohz long idle sleep: When the CPU which did the jiffies update last goes into a long idle sleep it drops the update jiffies duty so another CPU which is not idle can pick it up and keep jiffies going. Using the same value for both situations is wrong, as the CPU online code can see the -1 state when the timer of the newly onlined CPU is setup. The setup for a newly onlined CPU goes through periodic mode and can pick up the do_timer duty without being aware of the nohz / highres mode of the already running system. Use two separate states and make them constants to avoid magic numbers confusion. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/tick-internal.h')
-rw-r--r--kernel/time/tick-internal.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 6e9db9734aa..e18014fadf9 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -1,6 +1,10 @@
/*
* tick internal variable and functions used by low/high res code
*/
+
+#define TICK_DO_TIMER_NONE -1
+#define TICK_DO_TIMER_BOOT -2
+
DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
extern spinlock_t tick_device_lock;
extern ktime_t tick_next_period;