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| author | Venkatesh Pallipadi <venki@google.com> | 2010-10-04 17:03:23 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-10-18 20:52:29 +0200 |
| commit | d267f87fb8179c6dba03d08b91952e81bc3723c7 (patch) | |
| tree | ddcd2f7429964367fcb4ab1dd230a970452d72da | |
| parent | aa483808516ca5cacfa0e5849691f64fec25828e (diff) | |
| download | blackbird-op-linux-d267f87fb8179c6dba03d08b91952e81bc3723c7.tar.gz blackbird-op-linux-d267f87fb8179c6dba03d08b91952e81bc3723c7.zip | |
sched: Call tick_check_idle before __irq_enter
When CPU is idle and on first interrupt, irq_enter calls tick_check_idle()
to notify interruption from idle. But, there is a problem if this call
is done after __irq_enter, as all routines in __irq_enter may find
stale time due to yet to be done tick_check_idle.
Specifically, trace calls in __irq_enter when they use global clock and also
account_system_vtime change in this patch as it wants to use sched_clock_cpu()
to do proper irq timing.
But, tick_check_idle was moved after __irq_enter intentionally to
prevent problem of unneeded ksoftirqd wakeups by the commit ee5f80a:
irq: call __irq_enter() before calling the tick_idle_check
Impact: avoid spurious ksoftirqd wakeups
Moving tick_check_idle() before __irq_enter and wrapping it with
local_bh_enable/disable would solve both the problems.
Fixed-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-9-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | kernel/sched.c | 2 | ||||
| -rw-r--r-- | kernel/softirq.c | 12 |
2 files changed, 10 insertions, 4 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index bff9ef537df0..567f5cb9808c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1974,8 +1974,8 @@ void account_system_vtime(struct task_struct *curr) local_irq_save(flags); - now = sched_clock(); cpu = smp_processor_id(); + now = sched_clock_cpu(cpu); delta = now - per_cpu(irq_start_time, cpu); per_cpu(irq_start_time, cpu) = now; /* diff --git a/kernel/softirq.c b/kernel/softirq.c index 267f7b763ebb..79ee8f1fc0e7 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -296,10 +296,16 @@ void irq_enter(void) rcu_irq_enter(); if (idle_cpu(cpu) && !in_interrupt()) { - __irq_enter(); + /* + * Prevent raise_softirq from needlessly waking up ksoftirqd + * here, as softirq will be serviced on return from interrupt. + */ + local_bh_disable(); tick_check_idle(cpu); - } else - __irq_enter(); + _local_bh_enable(); + } + + __irq_enter(); } #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED |
