torture: Forgive -EBUSY from boottime CPU-hotplug operations

During boot, CPU hotplug is often disabled, for example by PCI probing.
On large systems that take substantial time to boot, this can result
in spurious RCU_HOTPLUG errors.  This commit therefore forgives any
boottime -EBUSY CPU-hotplug failures by adjusting counters to pretend
that the corresponding attempt never happened.  A non-splat record
of the failed attempt is emitted to the console with the added string
"(-EBUSY forgiven during boot)".

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/torture.c b/kernel/torture.c
index 7c13f55..e377b5b 100644 (file)
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -84,6 +84,7 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
 {
        unsigned long delta;
        int ret;
+       char *s;
        unsigned long starttime;
 
        if (!cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
@@ -99,10 +100,16 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
        (*n_offl_attempts)++;
        ret = cpu_down(cpu);
        if (ret) {
+               s = "";
+               if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
+                       // PCI probe frequently disables hotplug during boot.
+                       (*n_offl_attempts)--;
+                       s = " (-EBUSY forgiven during boot)";
+               }
                if (verbose)
                        pr_alert("%s" TORTURE_FLAG
-                                "torture_onoff task: offline %d failed: errno %d\n",
-                                torture_type, cpu, ret);
+                                "torture_onoff task: offline %d failed%s: errno %d\n",
+                                torture_type, cpu, s, ret);
        } else {
                if (verbose > 1)
                        pr_alert("%s" TORTURE_FLAG
@@ -137,6 +144,7 @@ bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
 {
        unsigned long delta;
        int ret;
+       char *s;
        unsigned long starttime;
 
        if (cpu_online(cpu) || !cpu_is_hotpluggable(cpu))
@@ -150,10 +158,16 @@ bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
        (*n_onl_attempts)++;
        ret = cpu_up(cpu);
        if (ret) {
+               s = "";
+               if (!rcu_inkernel_boot_has_ended() && ret == -EBUSY) {
+                       // PCI probe frequently disables hotplug during boot.
+                       (*n_onl_attempts)--;
+                       s = " (-EBUSY forgiven during boot)";
+               }
                if (verbose)
                        pr_alert("%s" TORTURE_FLAG
-                                "torture_onoff task: online %d failed: errno %d\n",
-                                torture_type, cpu, ret);
+                                "torture_onoff task: online %d failed%s: errno %d\n",
+                                torture_type, cpu, s, ret);
        } else {
                if (verbose > 1)
                        pr_alert("%s" TORTURE_FLAG