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authorIngo Molnar <mingo@kernel.org>2014-01-12 14:12:44 +0100
committerIngo Molnar <mingo@kernel.org>2014-01-12 14:12:44 +0100
commitdba861461f88c12249ac78fb877866c04f99deb3 (patch)
tree5812b143581bcc66c7c542f01ba0cb22e489b8e5 /kernel/time
parent0e6601eee039893a3f6420596ae4588d90d13cbe (diff)
parent228fdc083b017eaf90e578fa86fb1ecfd5ffae87 (diff)
Merge branch 'linus' into timers/core
Pick up the latest fixes and refresh the branch. Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-common.c15
-rw-r--r--kernel/time/tick-sched.c25
-rw-r--r--kernel/time/timekeeping.c2
3 files changed, 28 insertions, 14 deletions
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 64522ecdfe0e..162b03ab0ad2 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -33,6 +33,21 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
*/
ktime_t tick_next_period;
ktime_t tick_period;
+
+/*
+ * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
+ * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
+ * variable has two functions:
+ *
+ * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
+ * timekeeping lock all at once. Only the CPU which is assigned to do the
+ * update is handling it.
+ *
+ * 2) Hand off the duty in the NOHZ idle case by setting the value to
+ * TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
+ * at it will take over and keep the time keeping alive. The handover
+ * procedure also covers cpu hotplug.
+ */
int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
/*
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2afd43fca93b..52cee12b3302 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -361,8 +361,8 @@ void __init tick_nohz_init(void)
/*
* NO HZ enabled ?
*/
-int tick_nohz_enabled __read_mostly = 1;
-
+static int tick_nohz_enabled __read_mostly = 1;
+int tick_nohz_active __read_mostly;
/*
* Enable / Disable tickless mode
*/
@@ -461,7 +461,7 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
ktime_t now, idle;
- if (!tick_nohz_enabled)
+ if (!tick_nohz_active)
return -1;
now = ktime_get();
@@ -502,7 +502,7 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
ktime_t now, iowait;
- if (!tick_nohz_enabled)
+ if (!tick_nohz_active)
return -1;
now = ktime_get();
@@ -707,8 +707,10 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
return false;
}
- if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
+ if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) {
+ ts->sleep_length = (ktime_t) { .tv64 = NSEC_PER_SEC/HZ };
return false;
+ }
if (need_resched())
return false;
@@ -795,11 +797,6 @@ void tick_nohz_idle_enter(void)
local_irq_disable();
ts = &__get_cpu_var(tick_cpu_sched);
- /*
- * set ts->inidle unconditionally. even if the system did not
- * switch to nohz mode the cpu frequency governers rely on the
- * update of the idle time accounting in tick_nohz_start_idle().
- */
ts->inidle = 1;
__tick_nohz_idle_enter(ts);
@@ -968,7 +965,7 @@ static void tick_nohz_switch_to_nohz(void)
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
ktime_t next;
- if (!tick_nohz_enabled)
+ if (!tick_nohz_active)
return;
local_irq_disable();
@@ -976,7 +973,7 @@ static void tick_nohz_switch_to_nohz(void)
local_irq_enable();
return;
}
-
+ tick_nohz_active = 1;
ts->nohz_mode = NOHZ_MODE_LOWRES;
/*
@@ -1132,8 +1129,10 @@ void tick_setup_sched_timer(void)
}
#ifdef CONFIG_NO_HZ_COMMON
- if (tick_nohz_enabled)
+ if (tick_nohz_enabled) {
ts->nohz_mode = NOHZ_MODE_HIGHRES;
+ tick_nohz_active = 1;
+ }
#endif
}
#endif /* HIGH_RES_TIMERS */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 3abf53418b67..87b4f00284c9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1347,7 +1347,7 @@ static inline void old_vsyscall_fixup(struct timekeeper *tk)
tk->xtime_nsec -= remainder;
tk->xtime_nsec += 1ULL << tk->shift;
tk->ntp_error += remainder << tk->ntp_error_shift;
-
+ tk->ntp_error -= (1ULL << tk->shift) << tk->ntp_error_shift;
}
#else
#define old_vsyscall_fixup(tk)