Attachment 311400 Details for Bug 426861 – patch to reset monotonic_tv.* on backwards time jump

[patch] patch to reset monotonic_tv.* on backwards time jump

linux-2.6-xen-gettimeofday-jump.patch (text/plain), 1.15 KB, created by Rik van Riel on 2008-07-09 18:34:56 UTC

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Creator: Rik van Riel

Created: 2008-07-09 18:34:56 UTC

Size: 1.15 KB

patch

obsolete

>--- linux-2.6.18.noarch/arch/i386/kernel/time-xen.c.jumpback	2008-07-09 13:48:12.000000000 -0400
>+++ linux-2.6.18.noarch/arch/i386/kernel/time-xen.c	2008-07-09 14:04:16.000000000 -0400
>@@ -264,7 +264,8 @@
> {
> 	long wtm_nsec, xtime_nsec;
> 	time_t wtm_sec, xtime_sec;
>-	u64 tmp, wc_nsec;
>+	u64 tmp, wc_nsec, mt_nsec;
>+	unsigned long flags;
> 
> 	/* Adjust wall-clock time base based on wall_jiffies ticks. */
> 	wc_nsec = processed_system_time;
>@@ -283,6 +284,21 @@
> 	set_normalized_timespec(&xtime, xtime_sec, xtime_nsec);
> 	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
> 
>+	/*
>+	 * If the hypervisor jumped back in time, or we migrated to a
>+	 * hypervisor with a wall clock in the past, reset monotonic_tv
>+	 * so gettimeofday will not keep returning the same time for long
>+	 * periods. The 1/8 sec threshold is the maximum drift ntpd allows.
>+	 */
>+	spin_lock_irqsave(&monotonic_lock, flags);
>+	mt_nsec = (monotonic_tv.tv_sec * (u64)NSEC_PER_SEC) +
>+		   monotonic_tv.tv_usec;
>+	if (mt_nsec > wc_nsec + ((u64)NSEC_PER_SEC / 8)) {
>+		monotonic_tv.tv_sec = 0;
>+		monotonic_tv.tv_usec = 0;
>+	}
>+	spin_unlock_irqrestore(&monotonic_lock, flags);
>+
> 	ntp_clear();
> }
>

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Attachments on bug 426861: 311400 | 311410 | 319209