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x86: "nosmp" command line option should force the system into UP mode 

Bits set in cpu_possible_mask prior to the execution of
prefill_possible_map() (i.e.  when parsing ACPI or MPS tables) would
prevent the SMP alternatives logic from switching to UP mode, plus
unnecessary setup of per-CPU data for CPUs that can never come online.

Additionally, without CONFIG_HOTPLUG_CPU disabled CPUs can never come
online, and hence setting cpu_possible_mask bits for them is again a
simple waste of resources.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <201005241913.o4OJDH3Z010874@imap1.linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Jan Beulich 2010-05-24 12:13:17 -07:00 committed by H. Peter Anvin
parent b46fc5f235
commit 5f2eb55026
1 changed files with 23 additions and 3 deletions
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26
arch/x86/kernel/smpboot.c
View File

@ -1215,9 +1215,17 @@ __init void prefill_possible_map(void)
if (!num_processors)
num_processors = 1;
if (setup_possible_cpus == -1)
possible = num_processors + disabled_cpus;
else
i = setup_max_cpus ?: 1;
if (setup_possible_cpus == -1) {
possible = num_processors;
#ifdef CONFIG_HOTPLUG_CPU
if (setup_max_cpus)
possible += disabled_cpus;
#else
if (possible > i)
possible = i;
#endif
} else
possible = setup_possible_cpus;
total_cpus = max_t(int, possible, num_processors + disabled_cpus);
@ -1230,11 +1238,23 @@ __init void prefill_possible_map(void)
possible = nr_cpu_ids;
}
#ifdef CONFIG_HOTPLUG_CPU
if (!setup_max_cpus)
#endif
if (possible > i) {
printk(KERN_WARNING
"%d Processors exceeds max_cpus limit of %u\n",
possible, setup_max_cpus);
possible = i;
}
printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",
possible, max_t(int, possible - num_processors, 0));
for (i = 0; i < possible; i++)
set_cpu_possible(i, true);
for (; i < NR_CPUS; i++)
set_cpu_possible(i, false);
nr_cpu_ids = possible;
}