One wonders if it wouldn't be better to put the div in
gettimeofday() outside of the lock region, see below... It
makes the while condition even more unlikely.
-g
~snip~
> diff -urN -X dontdiff linux-2.5.59/arch/i386/kernel/time.c linux-2.5-frlock/arch/i386/kernel/time.c
> --- linux-2.5.59/arch/i386/kernel/time.c 2003-01-17 09:42:14.000000000 -0800
> +++ linux-2.5-frlock/arch/i386/kernel/time.c 2003-01-24 15:06:37.000000000 -0800
> @@ -70,7 +70,7 @@
>
> unsigned long cpu_khz; /* Detected as we calibrate the TSC */
>
> -extern rwlock_t xtime_lock;
> +extern frlock_t xtime_lock;
> extern unsigned long wall_jiffies;
>
> spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
> @@ -87,19 +87,21 @@
> */
> void do_gettimeofday(struct timeval *tv)
> {
> - unsigned long flags;
> + unsigned long seq;
++++> unsigned long xtimensec;
> unsigned long usec, sec;
>
> - read_lock_irqsave(&xtime_lock, flags);
> - usec = timer->get_offset();
> - {
> - unsigned long lost = jiffies - wall_jiffies;
> - if (lost)
> - usec += lost * (1000000 / HZ);
> - }
> - sec = xtime.tv_sec;
> - usec += (xtime.tv_nsec / 1000);
> - read_unlock_irqrestore(&xtime_lock, flags);
> + do {
> + seq = fr_read_begin(&xtime_lock);
> +
> + usec = timer->get_offset();
> + {
> + unsigned long lost = jiffies - wall_jiffies;
> + if (lost)
> + usec += lost * (1000000 / HZ);
> + }
> + sec = xtime.tv_sec;
----> + usec += (xtime.tv_nsec / 1000);
++++> + xtimensec = xtime.tv_nsec;
> + } while (unlikely(seq != fr_read_end(&xtime_lock)));
>
++++> usec += xtimensec / 1000;
> while (usec >= 1000000) {
> usec -= 1000000;
> @@ -112,7 +114,7 @@
>
> void do_settimeofday(struct timeval *tv)
> {
> - write_lock_irq(&xtime_lock);
> + fr_write_lock_irq(&xtime_lock);
> /*
> * This is revolting. We need to set "xtime" correctly. However, the
> * value in this location is the value at the most recent update of
> @@ -133,7 +135,7 @@
> time_status |= STA_UNSYNC;
> time_maxerror = NTP_PHASE_LIMIT;
> time_esterror = NTP_PHASE_LIMIT;
> - write_unlock_irq(&xtime_lock);
> + fr_write_unlock_irq(&xtime_lock);
> }
>
> /*
> @@ -279,12 +281,12 @@
> * the irq version of write_lock because as just said we have irq
> * locally disabled. -arca
> */
> - write_lock(&xtime_lock);
> + fr_write_lock(&xtime_lock);
>
> timer->mark_offset();
>
> do_timer_interrupt(irq, NULL, regs);
>
> - write_unlock(&xtime_lock);
> + fr_write_unlock(&xtime_lock);
>
> }
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Jan 31 2003 - 22:00:20 EST