#include <asm/mmu_context.h>
#include <asm/proto.h>
#include <asm/apic.h>
+#include <asm/nmi.h>
/*
* Some notes on x86 processor bugs affecting SMP operation:
*
* about nothing of note with C stepping upwards.
*/
+static atomic_t stopping_cpu = ATOMIC_INIT(-1);
+
/*
* this function sends a 'reschedule' IPI to another CPU.
* it goes straight through and wastes no time serializing
free_cpumask_var(allbutself);
}
+static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
+{
+ /* We are registered on stopping cpu too, avoid spurious NMI */
+ if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
+ return NMI_HANDLED;
+
+ stop_this_cpu(NULL);
+
+ return NMI_HANDLED;
+}
+
/*
* this function calls the 'stop' function on all other CPUs in the system.
*/
/*
* Use an own vector here because smp_call_function
* does lots of things not suitable in a panic situation.
- * On most systems we could also use an NMI here,
- * but there are a few systems around where NMI
- * is problematic so stay with an non NMI for now
- * (this implies we cannot stop CPUs spinning with irq off
- * currently)
+ */
+
+ /*
+ * 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);
/*
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)) {
+ 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;
+
+ /* 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);
+ }
+finish:
local_irq_save(flags);
disable_local_APIC();
local_irq_restore(flags);