diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 60830aa600ca8..5f93e4fcff32e 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -204,6 +204,10 @@ static void smp_callin(void) wmb(); + /* + * This runs the AP through all the cpuhp states to its target + * state (CPUHP_ONLINE in the case of serial bringup). + */ notify_cpu_starting(cpuid); /* @@ -231,17 +235,33 @@ static void notrace start_secondary(void *unused) load_cr3(swapper_pg_dir); __flush_tlb_all(); #endif + /* + * Sync point with do_wait_cpu_initialized(). On boot, all secondary + * CPUs reach this stage after receiving INIT/SIPI from do_cpu_up() + * in the x86/cpu:kick cpuhp stage. At the start of cpu_init() they + * will wait for do_wait_cpu_initialized() to set their bit in + * smp_callout_mask to release them. + */ cpu_init_secondary(); rcu_cpu_starting(raw_smp_processor_id()); x86_cpuinit.early_percpu_clock_init(); + + /* + * Sync point with do_wait_cpu_callin(). The AP doesn't wait here + * but just sets the bit to let the controlling CPU (BSP) know that + * it's got this far. + */ smp_callin(); enable_start_cpu0 = 0; /* otherwise gcc will move up smp_processor_id before the cpu_init */ barrier(); + /* - * Check TSC synchronization with the boot CPU: + * Check TSC synchronization with the boot CPU (or whichever CPU + * is controlling the bringup). It will do its part of this from + * do_wait_cpu_online(), making it an implicit sync point. */ check_tsc_sync_target(); @@ -254,6 +274,7 @@ static void notrace start_secondary(void *unused) * half valid vector space. */ lock_vector_lock(); + /* Sync point with do_wait_cpu_online() */ set_cpu_online(smp_processor_id(), true); lapic_online(); unlock_vector_lock(); @@ -1083,7 +1104,6 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle, unsigned long start_ip = real_mode_header->trampoline_start; unsigned long boot_error = 0; - unsigned long timeout; #ifdef CONFIG_X86_64 /* If 64-bit wakeup method exists, use the 64-bit mode trampoline IP */ @@ -1144,55 +1164,94 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle, boot_error = wakeup_cpu_via_init_nmi(cpu, start_ip, apicid, cpu0_nmi_registered); - if (!boot_error) { - /* - * Wait 10s total for first sign of life from AP - */ - boot_error = -1; - timeout = jiffies + 10*HZ; - while (time_before(jiffies, timeout)) { - if (cpumask_test_cpu(cpu, cpu_initialized_mask)) { - /* - * Tell AP to proceed with initialization - */ - cpumask_set_cpu(cpu, cpu_callout_mask); - boot_error = 0; - break; - } - schedule(); - } - } + return boot_error; +} - if (!boot_error) { - /* - * Wait till AP completes initial initialization - */ - while (!cpumask_test_cpu(cpu, cpu_callin_mask)) { - /* - * Allow other tasks to run while we wait for the - * AP to come online. This also gives a chance - * for the MTRR work(triggered by the AP coming online) - * to be completed in the stop machine context. - */ - schedule(); - } +static int do_wait_cpu_cpumask(unsigned int cpu, const struct cpumask *mask) +{ + unsigned long timeout; + + /* + * Wait up to 10s for the CPU to report in. + */ + timeout = jiffies + 10*HZ; + while (time_before(jiffies, timeout)) { + if (cpumask_test_cpu(cpu, mask)) + return 0; + + schedule(); } + return -1; +} - if (x86_platform.legacy.warm_reset) { - /* - * Cleanup possible dangling ends... - */ - smpboot_restore_warm_reset_vector(); +/* + * Bringup step two: Wait for the target AP to reach cpu_init_secondary() + * and thus wait_for_master_cpu(), then set cpu_callout_mask to allow it + * to proceed. The AP will then proceed past setting its 'callin' bit + * and end up waiting in check_tsc_sync_target() until we reach + * do_wait_cpu_online() to tend to it. + */ +static int do_wait_cpu_initialized(unsigned int cpu) +{ + /* + * Wait for first sign of life from AP. + */ + if (do_wait_cpu_cpumask(cpu, cpu_initialized_mask)) + return -1; + + cpumask_set_cpu(cpu, cpu_callout_mask); + return 0; +} + +/* + * Bringup step three: Wait for the target AP to reach smp_callin(). + * The AP is not waiting for us here so we don't need to parallelise + * this step. Not entirely clear why we care about this, since we just + * proceed directly to TSC synchronization which is the next sync + * point with the AP anyway. + */ +static int do_wait_cpu_callin(unsigned int cpu) +{ + /* + * Wait till AP completes initial initialization. + */ + return do_wait_cpu_cpumask(cpu, cpu_callin_mask); +} + +/* + * Bringup step four: Synchronize the TSC and wait for the target AP + * to reach set_cpu_online() in start_secondary(). + */ +static int do_wait_cpu_online(unsigned int cpu) +{ + unsigned long flags; + + /* + * Check TSC synchronization with the AP (keep irqs disabled + * while doing so): + */ + local_irq_save(flags); + check_tsc_sync_source(cpu); + local_irq_restore(flags); + + /* + * Wait for the AP to mark itself online. Not entirely + * clear why we care, since the generic cpuhp code will + * wait for it to each CPUHP_AP_ONLINE_IDLE before going + * ahead with the rest of the bringup anyway. + */ + while (!cpu_online(cpu)) { + cpu_relax(); + touch_nmi_watchdog(); } - return boot_error; + return 0; } -int native_cpu_up(unsigned int cpu, struct task_struct *tidle) +int do_cpu_up(unsigned int cpu, struct task_struct *tidle) { int apicid = apic->cpu_present_to_apicid(cpu); int cpu0_nmi_registered = 0; - unsigned long flags; int err, ret = 0; lockdep_assert_irqs_enabled(); @@ -1239,19 +1298,6 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) goto unreg_nmi; } - /* - * Check TSC synchronization with the AP (keep irqs disabled - * while doing so): - */ - local_irq_save(flags); - check_tsc_sync_source(cpu); - local_irq_restore(flags); - - while (!cpu_online(cpu)) { - cpu_relax(); - touch_nmi_watchdog(); - } - unreg_nmi: /* * Clean up the nmi handler. Do this after the callin and callout sync @@ -1263,6 +1309,34 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) return ret; } +int native_cpu_up(unsigned int cpu, struct task_struct *tidle) +{ + int ret; + + ret = do_cpu_up(cpu, tidle); + if (ret) + return ret; + + ret = do_wait_cpu_initialized(cpu); + if (ret) + return ret; + + ret = do_wait_cpu_callin(cpu); + if (ret) + return ret; + + ret = do_wait_cpu_online(cpu); + + if (x86_platform.legacy.warm_reset) { + /* + * Cleanup possible dangling ends... + */ + smpboot_restore_warm_reset_vector(); + } + + return ret; +} + /** * arch_disable_smp_support() - disables SMP support for x86 at runtime */