| From | Frederic Weisbecker <> | Subject | [PATCH 19/32] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset | Date | Mon, 15 Aug 2011 17:52:16 +0200 |
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Issue an IPI to restart the tick on a CPU that belongs to a cpuset when its nohz flag gets cleared.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Anton Blanchard <anton@au1.ibm.com> Cc: Avi Kivity <avi@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Menage <menage@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Pepper <lnxninja@linux.vnet.ibm.com> --- include/linux/cpuset.h | 1 + kernel/cpuset.c | 21 +++++++++++++++++++++ kernel/sched.c | 8 ++++++++ 3 files changed, 30 insertions(+), 0 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 799b9a4..7f9d78d 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -265,6 +265,7 @@ static inline bool cpuset_adaptive_nohz(void) } extern void cpuset_update_nohz(void); +extern void cpuset_exit_nohz_interrupt(void *unused); #else static inline void cpuset_update_nohz(void) { } diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 3135096..ee3b0d0 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1199,6 +1199,14 @@ static void cpuset_change_flag(struct task_struct *tsk, DEFINE_PER_CPU(int, cpu_adaptive_nohz_ref); +static void cpu_exit_nohz(int cpu) +{ + preempt_disable(); + smp_call_function_single(cpu, cpuset_exit_nohz_interrupt, + NULL, true); + preempt_enable(); +} + static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) { int cpu; @@ -1212,6 +1220,19 @@ static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) per_cpu(cpu_adaptive_nohz_ref, cpu) += 1; else per_cpu(cpu_adaptive_nohz_ref, cpu) -= 1; + + val = per_cpu(cpu_adaptive_nohz_ref, cpu); + + if (!val) { + /* + * The update to cpu_adaptive_nohz_ref must be + * visible right away. So that once we restart the tick + * from the IPI, it won't be stopped again due to cache + * update lag. + */ + smp_mb(); + cpu_exit_nohz(cpu); + } } } #else diff --git a/kernel/sched.c b/kernel/sched.c index 78ea0a5..75378be 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2513,6 +2513,14 @@ void cpuset_update_nohz(void) cpuset_nohz_restart_tick(); } +void cpuset_exit_nohz_interrupt(void *unused) +{ + if (!tick_nohz_adaptive_mode()) + return; + + cpuset_nohz_restart_tick(); +} + static void cpuset_nohz_task_switch(struct task_struct *next) { int cpu = smp_processor_id(); -- 1.7.5.4
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