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From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, tglx@linutronix.de
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
	rostedt@goodmis.org, bigeasy@linutronix.de, efault@gmx.de,
	max.byungchul.park@gmail.com
Subject: [PATCH 7/7] smp/hotplug: Hotplug state fail injection
Date: Wed, 20 Sep 2017 19:00:21 +0200
Message-ID: <20170920170546.972581715@infradead.org> (raw)
In-Reply-To: <20170920170014.548896195@infradead.org>


[-- Attachment #0: peterz-hotplug-6.patch --]
[-- Type: text/plain, Size: 3562 bytes --]

Add a sysfs file to one-time fail a specific state. This can be used
to test the state rollback code paths.

Something like this (hotplug-up.sh):

  #!/bin/bash

  echo 0 > /debug/sched_debug
  echo 1 > /debug/tracing/events/cpuhp/enable

  ALL_STATES=`cat /sys/devices/system/cpu/hotplug/states | cut -d':' -f1`
  STATES=${1:-$ALL_STATES}

  for state in $STATES
  do
	  echo 0 > /sys/devices/system/cpu/cpu1/online
	  echo 0 > /debug/tracing/trace
	  echo Fail state: $state
	  echo $state > /sys/devices/system/cpu/cpu1/hotplug/fail
	  cat /sys/devices/system/cpu/cpu1/hotplug/fail
	  echo 1 > /sys/devices/system/cpu/cpu1/online

	  cat /debug/tracing/trace > hotfail-${state}.trace

	  sleep 1
  done

Can be used to test for all possible rollback (barring multi-instance)
scenarios on CPU-up, CPU-down is a trivial modification of the above.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 include/linux/cpuhotplug.h |    3 +-
 kernel/cpu.c               |   60 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 61 insertions(+), 2 deletions(-)

--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -22,7 +22,8 @@
  */
 
 enum cpuhp_state {
-	CPUHP_OFFLINE,
+	CPUHP_INVALID = -1,
+	CPUHP_OFFLINE = 0,
 	CPUHP_CREATE_THREADS,
 	CPUHP_PERF_PREPARE,
 	CPUHP_PERF_X86_PREPARE,
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -52,6 +52,7 @@
 struct cpuhp_cpu_state {
 	enum cpuhp_state	state;
 	enum cpuhp_state	target;
+	enum cpuhp_state	fail;
 #ifdef CONFIG_SMP
 	struct task_struct	*thread;
 	bool			should_run;
@@ -67,7 +68,9 @@ struct cpuhp_cpu_state {
 #endif
 };
 
-static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
+static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
+	.fail = CPUHP_INVALID,
+};
 
 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
 static struct lockdep_map cpuhp_state_up_map =
@@ -180,6 +183,15 @@ static int cpuhp_invoke_callback(unsigne
 	int (*cb)(unsigned int cpu);
 	int ret, cnt;
 
+	if (st->fail == state) {
+		st->fail = CPUHP_INVALID;
+
+		if (!(bringup ? step->startup.single : step->teardown.single))
+			return 0;
+
+		return -EAGAIN;
+	}
+
 	if (!step->multi_instance) {
 		WARN_ON_ONCE(lastp && *lastp);
 		cb = bringup ? step->startup.single : step->teardown.single;
@@ -1806,9 +1818,55 @@ static ssize_t show_cpuhp_target(struct
 }
 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
 
+
+static ssize_t write_cpuhp_fail(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+	struct cpuhp_step *sp;
+	int fail, ret;
+
+	ret = kstrtoint(buf, 10, &fail);
+	if (ret)
+		return ret;
+
+	/*
+	 * Cannot fail STARTING/DYING callbacks.
+	 */
+	if (cpuhp_is_atomic_state(fail))
+		return -EINVAL;
+
+	/*
+	 * Cannot fail anything that doesn't have callbacks.
+	 */
+	mutex_lock(&cpuhp_state_mutex);
+	sp = cpuhp_get_step(fail);
+	if (!sp->startup.single && !sp->teardown.single)
+		ret = -EINVAL;
+	mutex_unlock(&cpuhp_state_mutex);
+	if (ret)
+		return ret;
+
+	st->fail = fail;
+
+	return count;
+}
+
+static ssize_t show_cpuhp_fail(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
+
+	return sprintf(buf, "%d\n", st->fail);
+}
+
+static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
+
 static struct attribute *cpuhp_cpu_attrs[] = {
 	&dev_attr_state.attr,
 	&dev_attr_target.attr,
+	&dev_attr_fail.attr,
 	NULL
 };
 

      parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-20 17:00 [PATCH 0/7] smp/hotplug rework / lockdep annotate Peter Zijlstra
2017-09-20 17:00 ` [PATCH 1/7] smp/hotplug: Add state diagram Peter Zijlstra
2017-09-20 17:00 ` [PATCH 2/7] smp/hotplug: Allow external multi-instance rollback Peter Zijlstra
2017-09-20 17:00 ` [PATCH 3/7] smp/hotplug: Rewrite AP state machine core Peter Zijlstra
2017-09-20 17:00 ` [PATCH 4/7] smp/hotplug: Callback vs state-machine consistency Peter Zijlstra
2017-09-20 17:00 ` [PATCH 5/7] smp/hotplug: Differentiate the AP completion between up and down Peter Zijlstra
2017-09-25  8:49   ` Byungchul Park
2017-09-20 17:00 ` [PATCH 6/7] smp/hotplug: Differentiate the AP-work lockdep class " Peter Zijlstra
2017-09-25  8:54   ` Byungchul Park
2017-09-25  9:16     ` Peter Zijlstra
2017-11-30 14:43   ` Lai Jiangshan
2017-09-20 17:00 ` Peter Zijlstra [this message]

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