rcutorture: Add a stall_cpu_repeat module parameter

This commit adds an stall_cpu_repeat kernel, which is also the
rcutorture.stall_cpu_repeat boot parameter, to test repeated CPU stalls.
Note that only the first stall will pay attention to the stall_cpu_irqsoff
module parameter.  For the second and subsequent stalls, interrupts will
be enabled.  This is helpful when testing the interaction between RCU
CPU stall warnings and CSD-lock stall warnings.

Reported-by: Rik van Riel <[email protected]>
Signed-off-by: "Paul E. McKenney" <[email protected]>
Signed-off-by: Neeraj Upadhyay <[email protected]>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f1384c7b59c9282fc6fb40569a92f6c13861bbb9..db1be767c91a4cac0ed20d154c67a34150617418 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5384,7 +5384,13 @@
                        Time to wait (s) after boot before inducing stall.
 
        rcutorture.stall_cpu_irqsoff= [KNL]
-                       Disable interrupts while stalling if set.
+                       Disable interrupts while stalling if set, but only
+                       on the first stall in the set.
+
+       rcutorture.stall_cpu_repeat= [KNL]
+                       Number of times to repeat the stall sequence,
+                       so that rcutorture.stall_cpu_repeat=3 will result
+                       in four stall sequences.
 
        rcutorture.stall_gp_kthread= [KNL]
                        Duration (s) of forced sleep within RCU

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 9a2ecb8b88ec1fd61bd7ee020bd0d120acc29e4d..4fd23cae0e9e49f434791f1bb9e30bd23baa72a4 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -115,6 +115,7 @@ torture_param(int, stall_cpu_holdoff, 10, "Time to wait before starting stall (s
 torture_param(bool, stall_no_softlockup, false, "Avoid softlockup warning during cpu stall.");
 torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
 torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
+torture_param(int, stall_cpu_repeat, 0, "Number of additional stalls after the first one.");
 torture_param(int, stall_gp_kthread, 0, "Grace-period kthread stall duration (s).");
 torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s");
 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
@@ -1393,7 +1394,8 @@ rcu_torture_writer(void *arg)
 
        // If a new stall test is added, this must be adjusted.
        if (stall_cpu_holdoff + stall_gp_kthread + stall_cpu)
-               stallsdone += (stall_cpu_holdoff + stall_gp_kthread + stall_cpu + 60) * HZ;
+               stallsdone += (stall_cpu_holdoff + stall_gp_kthread + stall_cpu + 60) *
+                             HZ * (stall_cpu_repeat + 1);
        VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
        if (!can_expedite)
                pr_alert("%s" TORTURE_FLAG
@@ -2391,7 +2393,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
                 "test_boost=%d/%d test_boost_interval=%d "
                 "test_boost_duration=%d shutdown_secs=%d "
                 "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
-                "stall_cpu_block=%d "
+                "stall_cpu_block=%d stall_cpu_repeat=%d "
                 "n_barrier_cbs=%d "
                 "onoff_interval=%d onoff_holdoff=%d "
                 "read_exit_delay=%d read_exit_burst=%d "
@@ -2403,7 +2405,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
                 test_boost, cur_ops->can_boost,
                 test_boost_interval, test_boost_duration, shutdown_secs,
                 stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
-                stall_cpu_block,
+                stall_cpu_block, stall_cpu_repeat,
                 n_barrier_cbs,
                 onoff_interval, onoff_holdoff,
                 read_exit_delay, read_exit_burst,
@@ -2481,19 +2483,11 @@ static struct notifier_block rcu_torture_stall_block = {
  * induces a CPU stall for the time specified by stall_cpu.  If a new
  * stall test is added, stallsdone in rcu_torture_writer() must be adjusted.
  */
-static int rcu_torture_stall(void *args)
+static void rcu_torture_stall_one(int rep, int irqsoff)
 {
        int idx;
-       int ret;
        unsigned long stop_at;
 
-       VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
-       if (rcu_cpu_stall_notifiers) {
-               ret = rcu_stall_chain_notifier_register(&rcu_torture_stall_block);
-               if (ret)
-                       pr_info("%s: rcu_stall_chain_notifier_register() returned %d, %sexpected.\n",
-                               __func__, ret, !IS_ENABLED(CONFIG_RCU_STALL_COMMON) ? "un" : "");
-       }
        if (stall_cpu_holdoff > 0) {
                VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
                schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
@@ -2513,12 +2507,12 @@ static int rcu_torture_stall(void *args)
                stop_at = ktime_get_seconds() + stall_cpu;
                /* RCU CPU stall is expected behavior in following code. */
                idx = cur_ops->readlock();
-               if (stall_cpu_irqsoff)
+               if (irqsoff)
                        local_irq_disable();
                else if (!stall_cpu_block)
                        preempt_disable();
-               pr_alert("%s start on CPU %d.\n",
-                         __func__, raw_smp_processor_id());
+               pr_alert("%s start stall episode %d on CPU %d.\n",
+                         __func__, rep + 1, raw_smp_processor_id());
                while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(), stop_at) &&
                       !kthread_should_stop())
                        if (stall_cpu_block) {
@@ -2530,12 +2524,42 @@ static int rcu_torture_stall(void *args)
                        } else if (stall_no_softlockup) {
                                touch_softlockup_watchdog();
                        }
-               if (stall_cpu_irqsoff)
+               if (irqsoff)
                        local_irq_enable();
                else if (!stall_cpu_block)
                        preempt_enable();
                cur_ops->readunlock(idx);
        }
+}
+
+/*
+ * CPU-stall kthread.  Invokes rcu_torture_stall_one() once, and then as many
+ * additional times as specified by the stall_cpu_repeat module parameter.
+ * Note that stall_cpu_irqsoff is ignored on the second and subsequent
+ * stall.
+ */
+static int rcu_torture_stall(void *args)
+{
+       int i;
+       int repeat = stall_cpu_repeat;
+       int ret;
+
+       VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
+       if (repeat < 0) {
+               repeat = 0;
+               WARN_ON_ONCE(IS_BUILTIN(CONFIG_RCU_TORTURE_TEST));
+       }
+       if (rcu_cpu_stall_notifiers) {
+               ret = rcu_stall_chain_notifier_register(&rcu_torture_stall_block);
+               if (ret)
+                       pr_info("%s: rcu_stall_chain_notifier_register() returned %d, %sexpected.\n",
+                               __func__, ret, !IS_ENABLED(CONFIG_RCU_STALL_COMMON) ? "un" : "");
+       }
+       for (i = 0; i <= repeat; i++) {
+               if (kthread_should_stop())
+                       break;
+               rcu_torture_stall_one(i, i == 0 ? stall_cpu_irqsoff : 0);
+       }
        pr_alert("%s end.\n", __func__);
        if (rcu_cpu_stall_notifiers && !ret) {
                ret = rcu_stall_chain_notifier_unregister(&rcu_torture_stall_block);