[PATCH] CPU hotplug: call check_tsc_sync_source() with irqs off
check_tsc_sync_source() depends on being called with irqs disabled (it
checks whether the TSC is coherent across two specific CPUs). This is
incidentally true during bootup, but not during cpu hotplug __cpu_up().
This got found via smp_processor_id() debugging.
disable irqs explicitly and remove the unconditional enabling of
interrupts. Add touch_nmi_watchdog() to the cpu_online_map busy loop.
this bug is present both on i386 and on x86_64.
Reported-by: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 9b0dd27..4ff55e6 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -45,6 +45,7 @@
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
+#include <linux/nmi.h>
#include <linux/delay.h>
#include <linux/mc146818rtc.h>
@@ -1278,8 +1279,9 @@
int __cpuinit __cpu_up(unsigned int cpu)
{
+ unsigned long flags;
#ifdef CONFIG_HOTPLUG_CPU
- int ret=0;
+ int ret = 0;
/*
* We do warm boot only on cpus that had booted earlier
@@ -1297,23 +1299,25 @@
/* In case one didn't come up */
if (!cpu_isset(cpu, cpu_callin_map)) {
printk(KERN_DEBUG "skipping cpu%d, didn't come online\n", cpu);
- local_irq_enable();
return -EIO;
}
- local_irq_enable();
-
per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
/* Unleash the CPU! */
cpu_set(cpu, smp_commenced_mask);
/*
- * Check TSC synchronization with the AP:
+ * 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_isset(cpu, cpu_online_map))
+ while (!cpu_isset(cpu, cpu_online_map)) {
cpu_relax();
+ touch_nmi_watchdog();
+ }
#ifdef CONFIG_X86_GENERICARCH
if (num_online_cpus() > 8 && genapic == &apic_default)
diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c
index 3544372..cd4643a 100644
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -923,8 +923,9 @@
*/
int __cpuinit __cpu_up(unsigned int cpu)
{
- int err;
int apicid = cpu_present_to_apicid(cpu);
+ unsigned long flags;
+ int err;
WARN_ON(irqs_disabled());
@@ -958,7 +959,9 @@
/*
* Make sure and check TSC sync:
*/
+ local_irq_save(flags);
check_tsc_sync_source(cpu);
+ local_irq_restore(flags);
while (!cpu_isset(cpu, cpu_online_map))
cpu_relax();
