From d267f87fb8179c6dba03d08b91952e81bc3723c7 Mon Sep 17 00:00:00 2001 From: Venkatesh Pallipadi Date: Mon, 4 Oct 2010 17:03:23 -0700 Subject: 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 Signed-off-by: Venkatesh Pallipadi Signed-off-by: Peter Zijlstra LKML-Reference: <1286237003-12406-9-git-send-email-venki@google.com> Signed-off-by: Ingo Molnar --- kernel/softirq.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'kernel/softirq.c') diff --git a/kernel/softirq.c b/kernel/softirq.c index 267f7b7..79ee8f1 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 -- cgit v1.1