1 files changed, 11 insertions, 15 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 79c7fe978b17..b1fffa21b9e4 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1368,7 +1368,6 @@ static inline void panic_on_rcu_stall(void)
 static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
 {
         int cpu;
-        long delta;
         unsigned long flags;
         unsigned long gpa;
         unsigned long j;
@@ -1381,18 +1380,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
         if (rcu_cpu_stall_suppress)
                 return;
 
-        /* Only let one CPU complain about others per time interval. */
-
-        raw_spin_lock_irqsave_rcu_node(rnp, flags);
-        delta = jiffies - READ_ONCE(rsp->jiffies_stall);
-        if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
-                raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-                return;
-        }
-        WRITE_ONCE(rsp->jiffies_stall,
-                   jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
-        raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-
         /*
          * OK, time to rat on our buddy...
          * See Documentation/RCU/stallwarn.txt for info on how to debug
@@ -1441,6 +1428,10 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
                         sched_show_task(current);
                 }
         }
+        /* Rewrite if needed in case of slow consoles. */
+        if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall)))
+                WRITE_ONCE(rsp->jiffies_stall,
+                           jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
 
         rcu_check_gp_kthread_starvation(rsp);
 
@@ -1485,6 +1476,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
         rcu_dump_cpu_stacks(rsp);
 
         raw_spin_lock_irqsave_rcu_node(rnp, flags);
+        /* Rewrite if needed in case of slow consoles. */
         if (ULONG_CMP_GE(jiffies, READ_ONCE(rsp->jiffies_stall)))
                 WRITE_ONCE(rsp->jiffies_stall,
                            jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
@@ -1508,6 +1500,7 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
         unsigned long gpnum;
         unsigned long gps;
         unsigned long j;
+        unsigned long jn;
         unsigned long js;
         struct rcu_node *rnp;
 
@@ -1546,14 +1539,17 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
             ULONG_CMP_GE(gps, js))
                 return; /* No stall or GP completed since entering function. */
         rnp = rdp->mynode;
+        jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
         if (rcu_gp_in_progress(rsp) &&
-            (READ_ONCE(rnp->qsmask) & rdp->grpmask)) {
+            (READ_ONCE(rnp->qsmask) & rdp->grpmask) &&
+            cmpxchg(&rsp->jiffies_stall, js, jn) == js) {
 
                 /* We haven't checked in, so go dump stack. */
                 print_cpu_stall(rsp);
 
         } else if (rcu_gp_in_progress(rsp) &&
-                   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
+                   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
+                   cmpxchg(&rsp->jiffies_stall, js, jn) == js) {
 
                 /* They had a few time units to dump stack, so complain. */
                 print_other_cpu_stall(rsp, gpnum);