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authorLinus Torvalds <torvalds@linux-foundation.org>2013-12-04 08:52:09 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-12-04 08:52:09 -0800
commit1ab231b274ba51a54acebec23c6aded0f3cdf54e (patch)
tree2ce15cb4ba9adf3e041eb9d1b26f63292c953094 /kernel
parentdea4f48a0a301b23c65af8e4fe8ccf360c272fbf (diff)
parent0e576acbc1d9600cf2d9b4a141a2554639959d50 (diff)
downloadop-kernel-dev-1ab231b274ba51a54acebec23c6aded0f3cdf54e.zip
op-kernel-dev-1ab231b274ba51a54acebec23c6aded0f3cdf54e.tar.gz
Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Thomas Gleixner: - timekeeping: Cure a subtle drift issue on GENERIC_TIME_VSYSCALL_OLD - nohz: Make CONFIG_NO_HZ=n and nohz=off command line option behave the same way. Fixes a long standing load accounting wreckage. - clocksource/ARM: Kconfig update to avoid ARM=n wreckage - clocksource/ARM: Fixlets for the AT91 and SH clocksource/clockevents - Trivial documentation update and kzalloc conversion from akpms pile * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: nohz: Fix another inconsistency between CONFIG_NO_HZ=n and nohz=off time: Fix 1ns/tick drift w/ GENERIC_TIME_VSYSCALL_OLD clocksource: arm_arch_timer: Hide eventstream Kconfig on non-ARM clocksource: sh_tmu: Add clk_prepare/unprepare support clocksource: sh_tmu: Release clock when sh_tmu_register() fails clocksource: sh_mtu2: Add clk_prepare/unprepare support clocksource: sh_mtu2: Release clock when sh_mtu2_register() fails ARM: at91: rm9200: switch back to clockevents_config_and_register tick: Document tick_do_timer_cpu timer: Convert kmalloc_node(...GFP_ZERO...) to kzalloc_node(...) NOHZ: Check for nohz active instead of nohz enabled
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcu/tree_plugin.h4
-rw-r--r--kernel/time/tick-common.c15
-rw-r--r--kernel/time/tick-sched.c25
-rw-r--r--kernel/time/timekeeping.c2
-rw-r--r--kernel/timer.c5
5 files changed, 32 insertions, 19 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 6abb03d..08a7652 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1632,7 +1632,7 @@ module_param(rcu_idle_gp_delay, int, 0644);
static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY;
module_param(rcu_idle_lazy_gp_delay, int, 0644);
-extern int tick_nohz_enabled;
+extern int tick_nohz_active;
/*
* Try to advance callbacks for all flavors of RCU on the current CPU, but
@@ -1729,7 +1729,7 @@ static void rcu_prepare_for_idle(int cpu)
int tne;
/* Handle nohz enablement switches conservatively. */
- tne = ACCESS_ONCE(tick_nohz_enabled);
+ tne = ACCESS_ONCE(tick_nohz_active);
if (tne != rdtp->tick_nohz_enabled_snap) {
if (rcu_cpu_has_callbacks(cpu, NULL))
invoke_rcu_core(); /* force nohz to see update. */
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 64522ec..162b03a 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 3612fc7..ea20f7d 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
*/
@@ -465,7 +465,7 @@ 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();
@@ -506,7 +506,7 @@ 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();
@@ -711,8 +711,10 @@ 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;
@@ -799,11 +801,6 @@ 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);
@@ -973,7 +970,7 @@ 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();
@@ -981,7 +978,7 @@ static void tick_nohz_switch_to_nohz(void)
local_irq_enable();
return;
}
-
+ tick_nohz_active = 1;
ts->nohz_mode = NOHZ_MODE_LOWRES;
/*
@@ -1139,8 +1136,10 @@ 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 3abf534..87b4f00 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)
diff --git a/kernel/timer.c b/kernel/timer.c
index 6582b82..accfd24 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1518,9 +1518,8 @@ static int init_timers_cpu(int cpu)
/*
* The APs use this path later in boot
*/
- base = kmalloc_node(sizeof(*base),
- GFP_KERNEL | __GFP_ZERO,
- cpu_to_node(cpu));
+ base = kzalloc_node(sizeof(*base), GFP_KERNEL,
+ cpu_to_node(cpu));
if (!base)
return -ENOMEM;
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