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Subject[RFC PATCH v2 08/12] x86: smp: use generic SMP stop common code
Date
Make x86 use the generic SMP-stop logic provided by common code unified
smp_send_stop() function.

Introduce needed arch_smp_stop_call()/arch_smp_cpus_stop_complete()
helpers that implement the backend architectures specific functionalities
previously provided by native_stop_other_cpus(): common logic is now
delegated to common SMP stop code.

Remove arch-specific smp_send_stop(), and redefine original function
native_stop_other_cpus() to rely instead on the unified common code
version of smp_send_stop(): native_stop_other_cpus() is anyway kept
since it is wired to smp_ops.stop_other_cpus() which get called at
reboot time with particular waiting settings.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
Note that in this patch we kept in use the original x86 local handling
of 'stopping_cpu' variable:

atomic_cmpxchg(&stopping_cpu, -1, 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/Kconfig | 1 +
arch/x86/include/asm/smp.h | 5 --
arch/x86/kernel/smp.c | 95 ++++++++++++++++----------------------
3 files changed, 41 insertions(+), 60 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 222855cc0158..0fcee2f03a5b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -92,6 +92,7 @@ config X86
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
+ select ARCH_USE_COMMON_SMP_STOP
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
select ARCH_WANTS_DYNAMIC_TASK_STRUCT
select ARCH_WANT_HUGE_PMD_SHARE
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index e1356a3b8223..5cf590259d68 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -67,11 +67,6 @@ extern void set_cpu_sibling_map(int cpu);
#ifdef CONFIG_SMP
extern struct smp_ops smp_ops;

-static inline void smp_send_stop(void)
-{
- smp_ops.stop_other_cpus(0);
-}
-
static inline void stop_other_cpus(void)
{
smp_ops.stop_other_cpus(1);
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 96421f97e75c..0942cae46fee 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -179,78 +179,63 @@ asmlinkage __visible void smp_reboot_interrupt(void)
irq_exit();
}

-static void native_stop_other_cpus(int wait)
+void arch_smp_stop_call(cpumask_t *cpus, unsigned int attempt_num)
{
- unsigned long flags;
- unsigned long timeout;
-
if (reboot_force)
return;

- /*
- * Use an own vector here because smp_call_function
- * does lots of things not suitable in a panic situation.
- */
-
- /*
- * We start by using the REBOOT_VECTOR irq.
- * The irq is treated as a sync point to allow critical
- * regions of code on other cpus to release their spin locks
- * and re-enable irqs. Jumping straight to an NMI might
- * accidentally cause deadlocks with further shutdown/panic
- * code. By syncing, we give the cpus up to one second to
- * finish their work before we force them off with the NMI.
- */
- if (num_online_cpus() > 1) {
- /* did someone beat us here? */
- if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
- return;
-
- /* sync above data before sending IRQ */
- wmb();
-
- apic->send_IPI_allbutself(REBOOT_VECTOR);
-
+ if (attempt_num == 1) {
/*
- * Don't wait longer than a second if the caller
- * didn't ask us to wait.
+ * We start by using the REBOOT_VECTOR irq.
+ * The irq is treated as a sync point to allow critical
+ * regions of code on other cpus to release their spin locks
+ * and re-enable irqs. Jumping straight to an NMI might
+ * accidentally cause deadlocks with further shutdown/panic
+ * code. By syncing, we give the cpus up to one second to
+ * finish their work before we force them off with the NMI.
*/
- timeout = USEC_PER_SEC;
- while (num_online_cpus() > 1 && (wait || timeout--))
- udelay(1);
- }
-
- /* if the REBOOT_VECTOR didn't work, try with the NMI */
- if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi)) {
- if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
- NMI_FLAG_FIRST, "smp_stop"))
- /* Note: we ignore failures here */
- /* Hope the REBOOT_IRQ is good enough */
- goto finish;
+
+ /* Used by NMI handler callback to skip the stopping_cpu. */
+ atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id());

/* sync above data before sending IRQ */
wmb();
-
- pr_emerg("Shutting down cpus with NMI\n");
-
- apic->send_IPI_allbutself(NMI_VECTOR);
-
- /*
- * Don't wait longer than a 10 ms if the caller
- * didn't ask us to wait.
- */
- timeout = USEC_PER_MSEC * 10;
- while (num_online_cpus() > 1 && (wait || timeout--))
- udelay(1);
+ apic->send_IPI_mask(cpus, REBOOT_VECTOR);
+ } else if (attempt_num > 1 && !smp_no_nmi_ipi) {
+ /* if the REBOOT_VECTOR didn't work, try with the NMI */
+
+ /* Don't wait longer than 10 ms when not asked to wait */
+ smp_stop_set_wait_timeout_us(USEC_PER_MSEC * 10);
+
+ /* Note: we ignore failures here */
+ /* Hope the REBOOT_IRQ was good enough */
+ if (!register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
+ NMI_FLAG_FIRST, "smp_stop")) {
+ /* sync above data before sending IRQ */
+ wmb();
+ pr_emerg("Shutting down cpus with NMI\n");
+ apic->send_IPI_mask(cpus, NMI_VECTOR);
+ }
}
+}
+
+void arch_smp_cpus_stop_complete(void)
+{
+ unsigned long flags;

-finish:
local_irq_save(flags);
disable_local_APIC();
mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
local_irq_restore(flags);
}

+static void native_stop_other_cpus(int wait)
+{
+ smp_stop_set_wait_forever(wait);
+ /* use common SMP stop code */
+ smp_send_stop();
+}
+
/*
* Reschedule call back. KVM uses this interrupt to force a cpu out of
* guest mode
--
2.17.1
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