1 files changed, 26 insertions, 1 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7f73c5edf8cf..9e3c20f117cd 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2950,6 +2950,9 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
  */
 void synchronize_sched_expedited(void)
 {
+        cpumask_var_t cm;
+        bool cma = false;
+        int cpu;
         long firstsnap, s, snap;
         int trycount = 0;
         struct rcu_state *rsp = &rcu_sched_state;
@@ -2984,11 +2987,26 @@ void synchronize_sched_expedited(void)
         }
         WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
 
+        /* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
+        cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
+        if (cma) {
+                cpumask_copy(cm, cpu_online_mask);
+                cpumask_clear_cpu(raw_smp_processor_id(), cm);
+                for_each_cpu(cpu, cm) {
+                        struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+                        if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
+                                cpumask_clear_cpu(cpu, cm);
+                }
+                if (cpumask_weight(cm) == 0)
+                        goto all_cpus_idle;
+        }
+
         /*
          * Each pass through the following loop attempts to force a
          * context switch on each CPU.
          */
-        while (try_stop_cpus(cpu_online_mask,
+        while (try_stop_cpus(cma ? cm : cpu_online_mask,
                              synchronize_sched_expedited_cpu_stop,
                              NULL) == -EAGAIN) {
                 put_online_cpus();
@@ -3000,6 +3018,7 @@ void synchronize_sched_expedited(void)
                         /* ensure test happens before caller kfree */
                         smp_mb__before_atomic(); /* ^^^ */
                         atomic_long_inc(&rsp->expedited_workdone1);
+                        free_cpumask_var(cm);
                         return;
                 }
 
@@ -3009,6 +3028,7 @@ void synchronize_sched_expedited(void)
                 } else {
                         wait_rcu_gp(call_rcu_sched);
                         atomic_long_inc(&rsp->expedited_normal);
+                        free_cpumask_var(cm);
                         return;
                 }
 
@@ -3018,6 +3038,7 @@ void synchronize_sched_expedited(void)
                         /* ensure test happens before caller kfree */
                         smp_mb__before_atomic(); /* ^^^ */
                         atomic_long_inc(&rsp->expedited_workdone2);
+                        free_cpumask_var(cm);
                         return;
                 }
 
@@ -3032,6 +3053,7 @@ void synchronize_sched_expedited(void)
                         /* CPU hotplug operation in flight, use normal GP. */
                         wait_rcu_gp(call_rcu_sched);
                         atomic_long_inc(&rsp->expedited_normal);
+                        free_cpumask_var(cm);
                         return;
                 }
                 snap = atomic_long_read(&rsp->expedited_start);
@@ -3039,6 +3061,9 @@ void synchronize_sched_expedited(void)
         }
         atomic_long_inc(&rsp->expedited_stoppedcpus);
 
+all_cpus_idle:
+        free_cpumask_var(cm);
+
         /*
          * Everyone up to our most recent fetch is covered by our grace
          * period.  Update the counter, but only if our work is still