Date: Tue, 17 Jan 2017 22:28:47 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Ian Lepore <ian@freebsd.org>, John Baldwin <jhb@freebsd.org> Cc: FreeBSD Current <freebsd-current@freebsd.org>, Konstantin Belousov <kib@freebsd.org> Subject: Re: Strange issue after early AP startup Message-ID: <11f27a15-f9bc-8988-a17e-78aeff1745fb@selasky.org> In-Reply-To: <1484682389.86335.166.camel@freebsd.org> References: <b9c53237-4b1a-a140-f692-bf5837060b18@selasky.org> <2215603.KuBd8pM5Pm@ralph.baldwin.cx> <3cbe6454-82cc-0592-4ee6-3c1552b19f9a@selasky.org> <4212167.Wq8tLU1ohU@ralph.baldwin.cx> <1484682389.86335.166.camel@freebsd.org>
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On 01/17/17 20:46, Ian Lepore wrote:
>>> Does this matter for the first tick? How often is configtimer() called?
>> >
>> > As I said, it is called at runtime when profclock is started / stopped, not
>> > just at boot. Those changes at runtime probably have existing callouts
>> > active and your change will not process any callouts until the next hardclock
>> > tick fires (but only because you are setting nextcallopt to the bogus
>> > 'next' value).
> On some platforms, configtimer() can be called quite often. Power
> saving modes can change the frequency of the timer, and systems that
> suppport such dynamic frequency scaling call configtimer()
> (via cpu_et_frequency()) to handle the changes.
Hi,
I propose the following patch then:
diff --git a/sys/kern/kern_clocksource.c b/sys/kern/kern_clocksource.c
index 7f7769d..5ae925b 100644
--- a/sys/kern/kern_clocksource.c
+++ b/sys/kern/kern_clocksource.c
@@ -511,8 +511,13 @@ configtimer(int start)
state->nexthard = next;
state->nextstat = next;
state->nextprof = next;
- state->nextcall = next;
- state->nextcallopt = next;
+ /*
+ * Force callout_process() to be called
+ * instantly, so that the correct value of
+ * "nextcall" can be computed:
+ */
+ state->nextcall = SBT_MAX;
+ state->nextcallopt = now + 1;
hardclock_sync(cpu);
}
busy = 0;
Then there is no problem having to wait for the next tick or anything,
like John Baldwin pointed out.
--HPS
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