rcu: Make rcutorture give diagnostics if CPU offline fails

This commit causes rcutorture to print the errno if cpu_down() fails
when the rcutorture "verbose" module parameter is specified.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index aaa7b9f3532a..9900f560f1bd 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -1502,6 +1502,7 @@ rcu_torture_onoff(void *arg)
         unsigned long delta;
         int maxcpu = -1;
         DEFINE_RCU_RANDOM(rand);
+        int ret;
         unsigned long starttime;
 
         VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
@@ -1522,7 +1523,13 @@ rcu_torture_onoff(void *arg)
                                          torture_type, cpu);
                         starttime = jiffies;
                         n_offline_attempts++;
-                        if (cpu_down(cpu) == 0) {
+                        ret = cpu_down(cpu);
+                        if (ret) {
+                                if (verbose)
+                                        pr_alert("%s" TORTURE_FLAG
+                                                 "rcu_torture_onoff task: offline %d failed: errno %d\n",
+                                                 torture_type, cpu, ret);
+                        } else {
                                 if (verbose)
                                         pr_alert("%s" TORTURE_FLAG
                                                  "rcu_torture_onoff task: offlined %d\n",