rcu: Eliminate check_cpu_stall() duplicate code

The code and comments of self-detected and other-detected RCU CPU stall
warnings are identical except the output function.  This commit therefore
refactors so as to consolidate the duplicate code.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index fc04a8d7ce96ebc9107f0e9e52407151267a2c2f..2443d1d4a6dcf766f259ef73f6d9fd79834a38e0 100644 (file)
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -711,7 +711,7 @@ static void print_cpu_stall(unsigned long gps)
 
 static void check_cpu_stall(struct rcu_data *rdp)
 {
-       bool didstall = false;
+       bool self_detected;
        unsigned long gs1;
        unsigned long gs2;
        unsigned long gps;
@@ -758,10 +758,10 @@ static void check_cpu_stall(struct rcu_data *rdp)
                return; /* No stall or GP completed since entering function. */
        rnp = rdp->mynode;
        jn = jiffies + ULONG_MAX / 2;
+       self_detected = READ_ONCE(rnp->qsmask) & rdp->grpmask;
        if (rcu_gp_in_progress() &&
-           (READ_ONCE(rnp->qsmask) & rdp->grpmask) &&
+           (self_detected || ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) &&
            cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
-
                /*
                 * If a virtual machine is stopped by the host it can look to
                 * the watchdog like an RCU stall. Check to see if the host
@@ -770,33 +770,21 @@ static void check_cpu_stall(struct rcu_data *rdp)
                if (kvm_check_and_clear_guest_paused())
                        return;
 
-               /* We haven't checked in, so go dump stack. */
-               print_cpu_stall(gps);
-               if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
-                       rcu_ftrace_dump(DUMP_ALL);
-               didstall = true;
-
-       } else if (rcu_gp_in_progress() &&
-                  ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
-                  cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
-
-               /*
-                * If a virtual machine is stopped by the host it can look to
-                * the watchdog like an RCU stall. Check to see if the host
-                * stopped the vm.
-                */
-               if (kvm_check_and_clear_guest_paused())
-                       return;
+               if (self_detected) {
+                       /* We haven't checked in, so go dump stack. */
+                       print_cpu_stall(gps);
+               } else {
+                       /* They had a few time units to dump stack, so complain. */
+                       print_other_cpu_stall(gs2, gps);
+               }
 
-               /* They had a few time units to dump stack, so complain. */
-               print_other_cpu_stall(gs2, gps);
                if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
                        rcu_ftrace_dump(DUMP_ALL);
-               didstall = true;
-       }
-       if (didstall && READ_ONCE(rcu_state.jiffies_stall) == jn) {
-               jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
-               WRITE_ONCE(rcu_state.jiffies_stall, jn);
+
+               if (READ_ONCE(rcu_state.jiffies_stall) == jn) {
+                       jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
+                       WRITE_ONCE(rcu_state.jiffies_stall, jn);
+               }
        }
 }