From: Frederic Weisbecker <[email protected]> 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 <[email protected]> Cc: Alessio Igor Bogani <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Avi Kivity <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Daniel Lezcano <[email protected]> Cc: Geoff Levand <[email protected]> Cc: Gilad Ben Yossef <[email protected]> Cc: Hakan Akkan <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Kevin Hilman <[email protected]> Cc: Max Krasnyansky <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Stephen Hemminger <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Sven-Thorsten Dietrich <[email protected]> Cc: Thomas Gleixner <[email protected]> --- include/linux/cpuset.h | 2 ++ kernel/cpuset.c | 25 +++++++++++++++++++++++-- kernel/time/tick-sched.c | 8 ++++++++ 3 files changed, 33 insertions(+), 2 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 7e7eb41..631968b 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -260,6 +260,8 @@ static inline bool cpuset_adaptive_nohz(void) */ return cpuset_cpu_adaptive_nohz(smp_processor_id()); } + +extern void cpuset_exit_nohz_interrupt(void *unused); #else static inline bool cpuset_cpu_adaptive_nohz(int cpu) { return false; } static inline bool cpuset_adaptive_nohz(void) { return false; } diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 6319d8e..1b67e5b 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1200,6 +1200,14 @@ static void cpuset_change_flag(struct task_struct *tsk, DEFINE_PER_CPU(atomic_t, 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; @@ -1211,9 +1219,22 @@ static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) for_each_cpu(cpu, cs->cpus_allowed) { atomic_t *ref = &per_cpu(cpu_adaptive_nohz_ref, cpu); if (is_adaptive_nohz(cs)) - atomic_inc(ref); + val = atomic_inc_return(ref); else - atomic_dec(ref); + val = atomic_dec_return(ref); + + 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. + * FIXME: We probably need more to ensure this value is really + * visible right away. + */ + smp_mb(); + cpu_exit_nohz(cpu); + } } } #else diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 0a5e650..de7de68 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -884,6 +884,14 @@ void tick_nohz_check_adaptive(void) } } +void cpuset_exit_nohz_interrupt(void *unused) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + + if (ts->tick_stopped && !is_idle_task(current)) + tick_nohz_restart_adaptive(); +} + void tick_nohz_post_schedule(void) { struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
