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Message-Id: <20240802003750.4134451-2-paulmck@kernel.org>
Date: Thu, 1 Aug 2024 17:37:49 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
kernel-team@...a.com,
rostedt@...dmis.org,
"Paul E. McKenney" <paulmck@...nel.org>,
Rik van Riel <riel@...riel.com>
Subject: [PATCH rcu 2/3] 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 <riel@...riel.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
.../admin-guide/kernel-parameters.txt | 8 ++-
kernel/rcu/rcutorture.c | 56 +++++++++++++------
2 files changed, 47 insertions(+), 17 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 35dd1e69b14d0..d30b81e693f9c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5388,7 +5388,13 @@
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 3dc7ef4af0eca..9dd6764e25f3d 100644
--- 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");
@@ -1385,7 +1386,8 @@ 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
@@ -2383,7 +2385,7 @@ 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 "
@@ -2395,7 +2397,7 @@ 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,
@@ -2473,19 +2475,11 @@ 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);
@@ -2505,12 +2499,12 @@ 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) {
@@ -2522,12 +2516,42 @@ 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() 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);
--
2.40.1
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