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-rw-r--r--arch/x86/kernel/cpu/mtrr/main.c23
-rw-r--r--include/linux/stop_machine.h2
-rw-r--r--kernel/stop_machine.c2
3 files changed, 26 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 929739a..3d17bc7 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
}
/**
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 092dc9b..14d3524 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -27,6 +27,8 @@ struct cpu_stop_work {
struct cpu_stop_done *done;
};
+extern struct mutex stop_cpus_mutex;
+
int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf);
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index e3516b2..0cae1cc 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -132,8 +132,8 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf);
}
+DEFINE_MUTEX(stop_cpus_mutex);
/* static data for stop_cpus */
-static DEFINE_MUTEX(stop_cpus_mutex);
static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work);
int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
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