Make x86 use the SMP common implementation of crash_smp_send_stop() and its generic logic, by removing the x86 crash_smp_send_stop() definition and providing the needed arch specific helpers.
Remove also redundant smp_ops.crash_stop_other_cpus(); add shared util function common_nmi_shootdown_cpus(), which is a generalization of the previous nmi_shootdown_cpus(), and it is used by architecture backend helper arch_smp_crash_call(). Modify original crash_nmi_callback() to properly set cpu offline flag and adding needed memory barriers. Modify original nmi_shootdown_cpus() to rely on common code logic provided by generic crash_smp_send_stop(): this was needed because the original nmi_shootdown_cpus() was used also on the emergency reboot path, employing a different callback. Reuse the same shootdown_callback mechanism to properly handle both a crash and an emergency reboot through the same common code crash path. Signed-off-by: Cristian Marussi <[email protected]> --- Note that in this patch we kept in use the original x86 local handling of 'crashing_cpu' variable: crashing_cpu = safe_smp_processor_id(); Instead, common SMP stop code could have been easily extended to keep and expose to architectures backends such value using some additional helper like smp_stop_get_stopping_cpu_id(). This has not been addressed in this series. --- arch/x86/include/asm/reboot.h | 2 ++ arch/x86/include/asm/smp.h | 1 - arch/x86/kernel/crash.c | 27 ++++--------------- arch/x86/kernel/reboot.c | 50 ++++++++++++++++++++++------------- arch/x86/kernel/smp.c | 3 --- 5 files changed, 38 insertions(+), 45 deletions(-) diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h index 04c17be9b5fd..a1a9cbed6df5 100644 --- a/arch/x86/include/asm/reboot.h +++ b/arch/x86/include/asm/reboot.h @@ -3,6 +3,7 @@ #define _ASM_X86_REBOOT_H #include <linux/kdebug.h> +#include <linux/cpumask.h> struct pt_regs; @@ -28,6 +29,7 @@ void __noreturn machine_real_restart(unsigned int type); typedef void (*nmi_shootdown_cb)(int, struct pt_regs*); void nmi_panic_self_stop(struct pt_regs *regs); void nmi_shootdown_cpus(nmi_shootdown_cb callback); +void common_nmi_shootdown_cpus(cpumask_t *cpus, nmi_shootdown_cb callback); void run_crash_ipi_callback(struct pt_regs *regs); #endif /* _ASM_X86_REBOOT_H */ diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index 5cf590259d68..684643ad71e4 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -49,7 +49,6 @@ struct smp_ops { void (*smp_cpus_done)(unsigned max_cpus); void (*stop_other_cpus)(int wait); - void (*crash_stop_other_cpus)(void); void (*smp_send_reschedule)(int cpu); int (*cpu_up)(unsigned cpu, struct task_struct *tidle); diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 2bf70a2fed90..8fff06c7cd26 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -96,34 +96,16 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs) disable_local_APIC(); } -void kdump_nmi_shootdown_cpus(void) +void arch_smp_crash_call(cpumask_t *cpus, unsigned int __unused) { - nmi_shootdown_cpus(kdump_nmi_callback); - - disable_local_APIC(); + common_nmi_shootdown_cpus(cpus, kdump_nmi_callback); } -/* Override the weak function in kernel/panic.c */ -void crash_smp_send_stop(void) +void arch_smp_cpus_crash_complete(void) { - static int cpus_stopped; - - if (cpus_stopped) - return; - - if (smp_ops.crash_stop_other_cpus) - smp_ops.crash_stop_other_cpus(); - else - smp_send_stop(); - - cpus_stopped = 1; + disable_local_APIC(); } -#else -void crash_smp_send_stop(void) -{ - /* There are no cpus to shootdown */ -} #endif void native_machine_crash_shutdown(struct pt_regs *regs) @@ -139,6 +121,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs) /* The kernel is broken so disable interrupts */ local_irq_disable(); + /* calling into SMP common stop code */ crash_smp_send_stop(); /* diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 09d6bded3c1e..69f894e28fec 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -799,7 +799,6 @@ int crashing_cpu = -1; static nmi_shootdown_cb shootdown_callback; -static atomic_t waiting_for_crash_ipi; static int crash_ipi_issued; static int crash_nmi_callback(unsigned int val, struct pt_regs *regs) @@ -819,7 +818,12 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs) shootdown_callback(cpu, regs); - atomic_dec(&waiting_for_crash_ipi); + /* ensure all shootdown writes are visible once cpu is seen offline */ + smp_wmb(); + set_cpu_online(cpu, false); + /* ensure all writes are globally visible before cpu parks */ + wmb(); + /* Assume hlt works */ halt(); for (;;) @@ -828,29 +832,44 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs) return NMI_HANDLED; } -static void smp_send_nmi_allbutself(void) -{ - apic->send_IPI_allbutself(NMI_VECTOR); -} - /* * Halt all other CPUs, calling the specified function on each of them * * This function can be used to halt all other CPUs on crash * or emergency reboot time. The function passed as parameter * will be called inside a NMI handler on all CPUs. + * + * It relies on crash_smp_send_stop() common code logic to shutdown CPUs. */ void nmi_shootdown_cpus(nmi_shootdown_cb callback) { - unsigned long msecs; + local_irq_disable(); + + shootdown_callback = callback; + /* ensure callback in place before calling into common crash code */ + wmb(); + /* call into common SMP Crash Stop to reuse the logic */ + crash_smp_send_stop(); +} + +/* + * Halt the specified @cpus, calling the provided @callback on each of them + * unless a shootdown_callback was already installed previously: this way + * we can handle here also the emergency reboot requests issued via + * nmi_shootdown_cpus() and routed via usual common code crash_smp_send_stop() + * + * Called by arch_smp_crash_call() arch-helper. + */ +void common_nmi_shootdown_cpus(cpumask_t *cpus, nmi_shootdown_cb callback) +{ local_irq_disable(); /* Make a note of crashing cpu. Will be used in NMI callback. */ crashing_cpu = safe_smp_processor_id(); - shootdown_callback = callback; - - atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1); + /* skip when the callback has been already set by nmi_shootdown_cpus */ + if (!shootdown_callback) + shootdown_callback = callback; /* Would it be better to replace the trap vector here? */ if (register_nmi_handler(NMI_LOCAL, crash_nmi_callback, NMI_FLAG_FIRST, "crash")) @@ -860,18 +879,11 @@ void nmi_shootdown_cpus(nmi_shootdown_cb callback) * out the NMI */ wmb(); - - smp_send_nmi_allbutself(); + apic->send_IPI_mask(cpus, NMI_VECTOR); /* Kick CPUs looping in NMI context. */ WRITE_ONCE(crash_ipi_issued, 1); - msecs = 1000; /* Wait at most a second for the other cpus to stop */ - while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) { - mdelay(1); - msecs--; - } - /* Leave the nmi callback set */ } diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c index 0942cae46fee..d718b185c6a9 100644 --- a/arch/x86/kernel/smp.c +++ b/arch/x86/kernel/smp.c @@ -295,9 +295,6 @@ struct smp_ops smp_ops = { .smp_cpus_done = native_smp_cpus_done, .stop_other_cpus = native_stop_other_cpus, -#if defined(CONFIG_KEXEC_CORE) - .crash_stop_other_cpus = kdump_nmi_shootdown_cpus, -#endif .smp_send_reschedule = native_smp_send_reschedule, .cpu_up = native_cpu_up, -- 2.17.1
