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SubjectRe: [PATCH] softlockup: stop spurious softlockup messages due to overflow
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Le lundi 15 mars 2010 à 14:01 +0000, Colin Ian King a écrit :
> Ensure additions on touch_ts do not overflow. This can occur when
> the top 32 bits of the TSC reach 0xffffffff causing additions to
> touch_ts to overflow and this in turn generates spurious softlockup
> warnings.
>
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> kernel/softlockup.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/softlockup.c b/kernel/softlockup.c
> index 0d4c789..90d9aa0 100644
> --- a/kernel/softlockup.c
> +++ b/kernel/softlockup.c
> @@ -111,10 +111,10 @@ int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
> void softlockup_tick(void)
> {
> int this_cpu = smp_processor_id();
> - unsigned long touch_ts = per_cpu(softlockup_touch_ts, this_cpu);
> + unsigned long long touch_ts = per_cpu(softlockup_touch_ts, this_cpu);
> unsigned long print_ts;
> struct pt_regs *regs = get_irq_regs();
> - unsigned long now;
> + unsigned long long now;
>
> /* Is detection switched off? */
> if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) {
> @@ -165,7 +165,7 @@ void softlockup_tick(void)
> per_cpu(softlockup_print_ts, this_cpu) = touch_ts;
>
> spin_lock(&print_lock);
> - printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
> + printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %llus! [%s:%d]\n",
> this_cpu, now - touch_ts,
> current->comm, task_pid_nr(current));
> print_modules();

This looks wrong, touch_ts is a long, not a long long.

You probably want to change the comparisons instead.

if (now > touch_ts + softlockup_thresh/2)
wake_up_process(per_cpu(softlockup_watchdog, this_cpu));
if (now <= (touch_ts + softlockup_thresh))
return;

->

if ((long)(now - touch_ts) > softlockup_thresh/2)
wake_up_process(per_cpu(softlockup_watchdog, this_cpu));
if ((long)(now - touch_ts) <= softlockup_thresh))
return;

Or use standard time_after()/time_before() macros.

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