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SubjectRe: [Bug 10648] CONFIG_PRINTK_TIME broken on git HEAD ?
From
Date
Subject: sched: fix sched_clock_cpu()
From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Make sched_clock_cpu() return 0 before it has been initialised and avoid
corrupting its state due to doing so.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/sched_clock.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
Index: linux-2.6/kernel/sched_clock.c
===================================================================
--- linux-2.6.orig/kernel/sched_clock.c 2008-05-13 18:40:35.000000000 +0200
+++ linux-2.6/kernel/sched_clock.c 2008-05-13 18:42:05.000000000 +0200
@@ -60,22 +60,26 @@
return &per_cpu(sched_clock_data, cpu);
}

+static __read_mostly int sched_clock_running;
+
void sched_clock_init(void)
{
u64 ktime_now = ktime_to_ns(ktime_get());
- u64 now = 0;
+ unsigned long now_jiffies = jiffies;
int cpu;

for_each_possible_cpu(cpu) {
struct sched_clock_data *scd = cpu_sdc(cpu);

scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
- scd->prev_jiffies = jiffies;
- scd->prev_raw = now;
- scd->tick_raw = now;
+ scd->prev_jiffies = now_jiffies;
+ scd->prev_raw = 0;
+ scd->tick_raw = 0;
scd->tick_gtod = ktime_now;
scd->clock = ktime_now;
}
+
+ sched_clock_running = 1;
}

/*
@@ -137,6 +141,9 @@
struct sched_clock_data *scd = cpu_sdc(cpu);
u64 now, clock;

+ if (unlikely(!sched_clock_running))
+ return 0ull;
+
/*
* Normally this is not called in NMI context - but if it is,
* trying to do any locking here is totally lethal.
@@ -182,6 +189,9 @@
struct sched_clock_data *scd = this_scd();
u64 now, now_gtod;

+ if (unlikely(!sched_clock_running))
+ return;
+
WARN_ON_ONCE(!irqs_disabled());

now = sched_clock();



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