summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/cpu/mtrr
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kernel/cpu/mtrr')
-rw-r--r--arch/x86/kernel/cpu/mtrr/main.c23
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 929739a653d1..3d17bc7f06e6 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -248,6 +248,25 @@ set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type typ
unsigned long flags;
int cpu;
+#ifdef CONFIG_SMP
+ /*
+ * If this cpu is not yet active, we are in the cpu online path. There
+ * can be no stop_machine() in parallel, as stop machine ensures this
+ * by using get_online_cpus(). We can skip taking the stop_cpus_mutex,
+ * as we don't need it and also we can't afford to block while waiting
+ * for the mutex.
+ *
+ * If this cpu is active, we need to prevent stop_machine() happening
+ * in parallel by taking the stop cpus mutex.
+ *
+ * Also, this is called in the context of cpu online path or in the
+ * context where cpu hotplug is prevented. So checking the active status
+ * of the raw_smp_processor_id() is safe.
+ */
+ if (cpu_active(raw_smp_processor_id()))
+ mutex_lock(&stop_cpus_mutex);
+#endif
+
preempt_disable();
data.smp_reg = reg;
@@ -330,6 +349,10 @@ set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type typ
local_irq_restore(flags);
preempt_enable();
+#ifdef CONFIG_SMP
+ if (cpu_active(raw_smp_processor_id()))
+ mutex_unlock(&stop_cpus_mutex);
+#endif
}
/**