Messages in this thread Patch in this message | | | Date | Mon, 1 Feb 2010 14:02:45 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] panic: Fix panic_timeout accuracy when running on a hypervisor |
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On Mon, 1 Feb 2010 15:14:30 +1100 Anton Blanchard <anton@samba.org> wrote:
> > I've had some complaints about panic_timeout being wildly innacurate on > shared processor PowerPC partitions (a 3 minute panic_timeout taking 30 > minutes). > > The problem is we loop on mdelay(1) and with a 1ms in 10ms hypervisor > timeslice each of these will take 10ms (ie 10x) longer. I expect other > platforms with shared processor hypervisors will see the same issue. > > This patch keeps the old behaviour if we have a panic_blink (only keyboard > LEDs right now) and does 1 second mdelays if we don't. > > ... > > +static void panic_blink_one_second(void) > +{ > + static long i = 0, end;
I assumed the `static' was a brainfart and removed it?
> + if (panic_blink) { > + end = i + MSEC_PER_SEC; > + > + while (i < end) { > + i += panic_blink(i); > + mdelay(1); > + i++; > + } > + } else { > + /* > + * When running under a hypervisor a small mdelay may get > + * rounded up to the hypervisor timeslice. For example, with > + * a 1ms in 10ms hypervisor timeslice we might inflate a > + * mdelay(1) loop by 10x. > + * > + * If we have nothing to blink, spin on 1 second calls to > + * mdelay to avoid this. > + */ > + mdelay(MSEC_PER_SEC); > + } > +}
In fact we can simplify it a bit:
--- a/kernel/panic.c~panic-fix-panic_timeout-accuracy-when-running-on-a-hypervisor-fix +++ a/kernel/panic.c @@ -42,12 +42,10 @@ EXPORT_SYMBOL(panic_blink); static void panic_blink_one_second(void) { - static long i = 0, end; - if (panic_blink) { - end = i + MSEC_PER_SEC; + long i = 0; - while (i < end) { + while (i < MSEC_PER_SEC) { i += panic_blink(i); mdelay(1); i++; _ Why does it do the mdelay() as well as calling panic_blink()? hm, because the old code did. I guess it doesn't trust panic_blink().
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