Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 30/33] sched: Debug nohz rq clock | Date | Tue, 8 Jan 2013 03:08:30 +0100 |
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The runqueue clock is supposed to be periodically updated by the tick. On full dynticks CPU we call update_nohz_rq_clock() before reading it. Now the scheduler code is complicated enough that we may miss some update_nohz_rq_clock() calls before reading the runqueue clock.
This therefore introduce a new debugging feature that detects when the rq clock is stale due to missing updates on full dynticks CPUs.
This can be later expanded to debug stale clocks on dynticks-idle CPUs.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Alessio Igor Bogani <abogani@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> --- kernel/sched/sched.h | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index e1bac76..0fef0b3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -502,16 +502,39 @@ DECLARE_PER_CPU(struct rq, runqueues); #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #define raw_rq() (&__raw_get_cpu_var(runqueues)) +static inline void rq_clock_check(struct rq *rq) +{ +#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_NO_HZ_FULL) + unsigned long long clock; + unsigned long flags; + int cpu; + + cpu = cpu_of(rq); + if (!tick_nohz_full_cpu(cpu) || rq->curr == rq->idle) + return; + + local_irq_save(flags); + clock = sched_clock_cpu(cpu_of(rq)); + local_irq_restore(flags); + + if (abs(clock - rq->clock) > (TICK_NSEC * 3)) + WARN_ON_ONCE(1); +#endif +} + static inline u64 rq_clock(struct rq *rq) { + rq_clock_check(rq); return rq->clock; } static inline u64 rq_clock_task(struct rq *rq) { + rq_clock_check(rq); return rq->clock_task; } + #ifdef CONFIG_SMP #define rcu_dereference_check_sched_domain(p) \ -- 1.7.5.4
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