[tip:x86/urgent] x86: "nosmp" command line option should force the system into UP mode
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From: tip-bot for Jan Beulich on 24 May 2010 19:10 Commit-ID: 5f2eb55026c91f8400ab4469aff88b2e201b5616 Gitweb: http://git.kernel.org/tip/5f2eb55026c91f8400ab4469aff88b2e201b5616 Author: Jan Beulich <JBeulich(a)novell.com> AuthorDate: Mon, 24 May 2010 12:13:17 -0700 Committer: H. Peter Anvin <hpa(a)linux.intel.com> CommitDate: Mon, 24 May 2010 13:31:52 -0700 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(a)novell.com> LKML-Reference: <201005241913.o4OJDH3Z010874(a)imap1.linux-foundation.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Signed-off-by: H. Peter Anvin <hpa(a)linux.intel.com> --- arch/x86/kernel/smpboot.c | 26 +++++++++++++++++++++++--- 1 files changed, 23 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 763d815..37462f1 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |