sched: fix init_idle()'s use of sched_clock()
Maciej Rutecki reported:
> I have this bug during suspend to disk:
>
> [ 188.592151] Enabling non-boot CPUs ...
> [ 188.592151] SMP alternatives: switching to SMP code
> [ 188.666058] BUG: using smp_processor_id() in preemptible
> [00000000]
> code: suspend_to_disk/2934
> [ 188.666064] caller is native_sched_clock+0x2b/0x80
Which, as noted by Linus, was caused by me, via:
7cbaef9c "sched: optimize sched_clock() a bit"
Move the rq locking a bit earlier in the initialization sequence,
that will make the sched_clock() call in init_idle() non-preemptible.
Reported-by: Maciej Rutecki <maciej.rutecki@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 3bafbe3..c94baf2 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5870,6 +5870,8 @@
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
+ spin_lock_irqsave(&rq->lock, flags);
+
__sched_fork(idle);
idle->se.exec_start = sched_clock();
@@ -5877,7 +5879,6 @@
idle->cpus_allowed = cpumask_of_cpu(cpu);
__set_task_cpu(idle, cpu);
- spin_lock_irqsave(&rq->lock, flags);
rq->curr = rq->idle = idle;
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
idle->oncpu = 1;