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-rw-r--r--kernel/stop_machine.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index c530bc5be7cf..84571e09c907 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -20,6 +20,7 @@
#include <linux/kallsyms.h>
#include <linux/smpboot.h>
#include <linux/atomic.h>
+#include <linux/lglock.h>
/*
* Structure to determine completion condition and record errors. May
@@ -43,6 +44,14 @@ static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
static DEFINE_PER_CPU(struct task_struct *, cpu_stopper_task);
static bool stop_machine_initialized = false;
+/*
+ * Avoids a race between stop_two_cpus and global stop_cpus, where
+ * the stoppers could get queued up in reverse order, leading to
+ * system deadlock. Using an lglock means stop_two_cpus remains
+ * relatively cheap.
+ */
+DEFINE_STATIC_LGLOCK(stop_cpus_lock);
+
static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
{
memset(done, 0, sizeof(*done));
@@ -276,6 +285,7 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
return -ENOENT;
}
+ lg_local_lock(&stop_cpus_lock);
/*
* Queuing needs to be done by the lowest numbered CPU, to ensure
* that works are always queued in the same order on every CPU.
@@ -284,6 +294,7 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
smp_call_function_single(min(cpu1, cpu2),
&irq_cpu_stop_queue_work,
&call_args, 0);
+ lg_local_unlock(&stop_cpus_lock);
preempt_enable();
wait_for_completion(&done.completion);
@@ -335,10 +346,10 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask,
* preempted by a stopper which might wait for other stoppers
* to enter @fn which can lead to deadlock.
*/
- preempt_disable();
+ lg_global_lock(&stop_cpus_lock);
for_each_cpu(cpu, cpumask)
cpu_stop_queue_work(cpu, &per_cpu(stop_cpus_work, cpu));
- preempt_enable();
+ lg_global_unlock(&stop_cpus_lock);
}
static int __stop_cpus(const struct cpumask *cpumask,