diff options
| author | Venkatesh Pallipadi <venki@google.com> | 2011-02-10 10:23:28 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-02-17 15:37:27 -0800 |
| commit | 19d3e3cbe91fd8c800654ff2b54cdb993cdf0336 (patch) | |
| tree | 047ef8fcdaf133f83cafec726dabd71eb4c3dffe | |
| parent | c8c885599ad2115e0a2fe661c2fb6ba4edc92c19 (diff) | |
sched: Call tick_check_idle before __irq_enter
Commit: d267f87fb8179c6dba03d08b91952e81bc3723c7 upstream
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>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -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 4f8609420bec..c7f69fe024e1 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1872,8 +1872,8 @@ 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 0a617de20434..04a0252d7d24 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 |