diff options
Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r-- | arch/x86/kernel/alternative.c | 40 |
1 files changed, 27 insertions, 13 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index d6405e0842b5..45d79ea890ae 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -273,6 +273,7 @@ struct smp_alt_module { }; static LIST_HEAD(smp_alt_modules); static DEFINE_SPINLOCK(smp_alt); +static int smp_mode = 1; /* protected by smp_alt */ void alternatives_smp_module_add(struct module *mod, char *name, void *locks, void *locks_end, @@ -341,12 +342,13 @@ void alternatives_smp_switch(int smp) #ifdef CONFIG_LOCKDEP /* - * A not yet fixed binutils section handling bug prevents - * alternatives-replacement from working reliably, so turn - * it off: + * Older binutils section handling bug prevented + * alternatives-replacement from working reliably. + * + * If this still occurs then you should see a hang + * or crash shortly after this line: */ - printk("lockdep: not fixing up alternatives.\n"); - return; + printk("lockdep: fixing up alternatives.\n"); #endif if (noreplace_smp || smp_alt_once) @@ -354,21 +356,29 @@ void alternatives_smp_switch(int smp) BUG_ON(!smp && (num_online_cpus() > 1)); spin_lock_irqsave(&smp_alt, flags); - if (smp) { + + /* + * Avoid unnecessary switches because it forces JIT based VMs to + * throw away all cached translations, which can be quite costly. + */ + if (smp == smp_mode) { + /* nothing */ + } else if (smp) { printk(KERN_INFO "SMP alternatives: switching to SMP code\n"); - clear_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability); - clear_bit(X86_FEATURE_UP, cpu_data(0).x86_capability); + clear_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); + clear_cpu_cap(&cpu_data(0), X86_FEATURE_UP); list_for_each_entry(mod, &smp_alt_modules, next) alternatives_smp_lock(mod->locks, mod->locks_end, mod->text, mod->text_end); } else { printk(KERN_INFO "SMP alternatives: switching to UP code\n"); - set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability); - set_bit(X86_FEATURE_UP, cpu_data(0).x86_capability); + set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); + set_cpu_cap(&cpu_data(0), X86_FEATURE_UP); list_for_each_entry(mod, &smp_alt_modules, next) alternatives_smp_unlock(mod->locks, mod->locks_end, mod->text, mod->text_end); } + smp_mode = smp; spin_unlock_irqrestore(&smp_alt, flags); } @@ -431,8 +441,9 @@ void __init alternative_instructions(void) if (smp_alt_once) { if (1 == num_possible_cpus()) { printk(KERN_INFO "SMP alternatives: switching to UP code\n"); - set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability); - set_bit(X86_FEATURE_UP, cpu_data(0).x86_capability); + set_cpu_cap(&boot_cpu_data, X86_FEATURE_UP); + set_cpu_cap(&cpu_data(0), X86_FEATURE_UP); + alternatives_smp_unlock(__smp_locks, __smp_locks_end, _text, _etext); } @@ -440,7 +451,10 @@ void __init alternative_instructions(void) alternatives_smp_module_add(NULL, "core kernel", __smp_locks, __smp_locks_end, _text, _etext); - alternatives_smp_switch(0); + + /* Only switch to UP mode if we don't immediately boot others */ + if (num_possible_cpus() == 1 || setup_max_cpus <= 1) + alternatives_smp_switch(0); } #endif apply_paravirt(__parainstructions, __parainstructions_end); |