Date: Tue, 27 Jan 2004 21:58:15 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Bart Samwel <bart@samwel.tk>
Cc: Huw Rogers <count0@localnet.com>, linux-kernel@vger.kernel.org,
       linux-laptop@mobilix.org
Subject: Re: 2.6.2-rc1 / ACPI sleep / irqbalance / kirqd / pentium 4 HT problems on Uniwill N258SA0
Message-ID: <20040127205815.GA19011@elf.ucw.cz>
References: <20040124233749.5637.COUNT0@localnet.com> <20040127083936.GA18246@elf.ucw.cz> <401685F9.6000904@samwel.tk>
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Hi!

> >>Anyway, sleep/suspend/standby functionality (important to most laptop
> >>users, need to close the lid and go): This checkin to
> >>kernel/power/main.c seems to disable suspend with SMP (!?):
> >>
> >>--- 1.3/kernel/power/main.c	Sat Jan 24 20:44:47 2004
> >>+++ 1.4/kernel/power/main.c	Sat Jan 24 20:44:47 2004
> >>@@ -172,6 +172,12 @@
> >> 	if (down_trylock(&pm_sem))
> >> 		return -EBUSY;
> >>
> >>+	/* Suspend is hard to get right on SMP. */
> >>+	if (num_online_cpus() != 1) {
> >>+		error = -EPERM;
> >>+		goto Unlock;
> >>+	}
> >>+
> >> 	if ((error = suspend_prepare(state)))
> >> 		goto Unlock;
> >>
> >>... which, given the prevalence of hyperthreaded CPUs on laptops, is
> >>fighting a trend. I backed out the above with a #if 0 then tried echo -n
> >>1>/proc/acpi/sleep again. This time I got:
> >
> >
> > Well, no sleep developers have SMP or HT machines, AFAICT.
> >
> > If you back that out... well you are on your own.
> 
> Just a random thought: if I understand it correctly, CPU hotplugging is 
> intended to be able to take CPUs online and offline one by one, am I 
> right? Well, when that infrastructure's ready, this can probably be made 
> to work for SMP by taking all the other CPUs offline first. They're all 
> going to go offline because of the suspend anyway, so it shouldn't make 
> much difference. :)

That was original plan, but CPU hotplug is unlikely to get into 2.6,
AFAICT. (And Nigel has another solution).

								Pavel

-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]
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