Messages in this thread Patch in this message | | | Date | Sun, 5 Oct 2008 16:52:24 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: <PING> Re: [patch x86/core] x86: allow number of additional hotplug CPUs to be set at compile time |
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On Sun, 5 Oct 2008, Ingo Molnar wrote: > * Chuck Ebbert <cebbert@redhat.com> wrote: > > > Yes, it works and I don't see how it could cause any problems. > > > > Ingo, can we get this in 2.6.27? You can drop my original patch. > > > > Tested-by: Chuck Ebbert <cebbert@redhat.com> > > looks good, applied to tip/x86/core, thanks!
No, this patch is horrible.
The correct check is num_present_cpus(). There is no need to make the weird additional_cpus hackery globally available.
Btw, additional_cpus has interesting properties. Providing a negative number < -1 on the kernel command line - happened due to a typo - explodes in early boot, which is not really surprising, but should be sanity checked.
Thanks,
tglx ----------------> Subject: x86: make UP alternatives switch depend on present cpus From: Thomas Gleixner <tglx@linutronix.de> Date: Sun, 05 Oct 2008 16:45:22 +0200
num_possible_cpus() can be > 1 when disabled CPUs have been accounted.
Disabled CPUs are not in the cpu_present_map, so we can use num_present_cpus() as a safe indicator to switch to UP alternatives.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index fb04e49..a84ac7b 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -444,7 +444,7 @@ void __init alternative_instructions(void) _text, _etext); /* Only switch to UP mode if we don't immediately boot others */ - if (num_possible_cpus() == 1 || setup_max_cpus <= 1) + if (num_present_cpus() == 1 || setup_max_cpus <= 1) alternatives_smp_switch(0); } #endif
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