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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Sebastian Siewior <bigeasy@linutronix.de>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	"David S. Miller" <davem@davemloft.net>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Len Brown <lenb@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Tejun Heo <tj@kernel.org>, Tony Luck <tony.luck@intel.com>,
	Viresh Kumar <viresh.kumar@linaro.org>
Subject: [patch 02/13] workqueue: Provide work_on_cpu_safe()
Date: Wed, 12 Apr 2017 22:07:28 +0200
Message-ID: <20170412201042.262610721@linutronix.de> (raw)
In-Reply-To: <20170412200726.941336635@linutronix.de>


[-- Attachment #0: workqueue--Provide-work_on_cpu_safe--.patch --]
[-- Type: text/plain, Size: 1942 bytes --]

work_on_cpu() is not protected against CPU hotplug. For code which requires
to be either executed on an online CPU or to fail if the CPU is not
available the callsite would have to protect against CPU hotplug.

Provide a function which does get/put_online_cpus() around the call to
work_on_cpu() and fails the call with -ENODEV if the target CPU is not
online.

Preparatory patch to convert several racy task affinity manipulations.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
---
 include/linux/workqueue.h |    5 +++++
 kernel/workqueue.c        |   23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+)

--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -608,8 +608,13 @@ static inline long work_on_cpu(int cpu,
 {
 	return fn(arg);
 }
+static inline long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
+{
+	return fn(arg);
+}
 #else
 long work_on_cpu(int cpu, long (*fn)(void *), void *arg);
+long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg);
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_FREEZER
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4735,6 +4735,29 @@ long work_on_cpu(int cpu, long (*fn)(voi
 	return wfc.ret;
 }
 EXPORT_SYMBOL_GPL(work_on_cpu);
+
+/**
+ * work_on_cpu_safe - run a function in thread context on a particular cpu
+ * @cpu: the cpu to run on
+ * @fn:  the function to run
+ * @arg: the function argument
+ *
+ * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
+ * any locks which would prevent @fn from completing.
+ *
+ * Return: The value @fn returns.
+ */
+long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
+{
+	long ret = -ENODEV;
+
+	get_online_cpus();
+	if (cpu_online(cpu))
+		ret = work_on_cpu(cpu, fn, arg);
+	put_online_cpus();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(work_on_cpu_safe);
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_FREEZER

  parent reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-12 20:07 [patch 00/13] sched/treewide: Clean up various racy task affinity issues Thomas Gleixner
2017-04-12 20:07 ` [patch 01/13] ia64/topology: Remove cpus_allowed manipulation Thomas Gleixner
2017-04-15 14:15   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` Thomas Gleixner [this message]
2017-04-13 11:11   ` [patch 02/13] workqueue: Provide work_on_cpu_safe() Dou Liyang
2017-04-13 21:28     ` Thomas Gleixner
2017-04-14  4:18   ` Tejun Heo
2017-04-14  8:54   ` Peter Zijlstra
2017-04-14  9:51     ` Thomas Gleixner
2017-04-14  9:56       ` Peter Zijlstra
2017-04-15 14:16   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 03/13] ia64/salinfo: Replace racy task affinity logic Thomas Gleixner
2017-04-15 14:17   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 04/13] ia64/sn/hwperf: " Thomas Gleixner
2017-04-12 20:53   ` [patch V 2 " Thomas Gleixner
2017-04-15 14:17     ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 05/13] powerpc/smp: Replace open coded " Thomas Gleixner
2017-04-13  5:47   ` Michael Ellerman
2017-04-15 14:18   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 06/13] sparc/sysfs: Replace racy " Thomas Gleixner
2017-04-13  1:52   ` David Miller
2017-04-13  8:17     ` [patch V2 " Thomas Gleixner
2017-04-15 14:18       ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 07/13] ACPI/processor: Fix error handling in __acpi_processor_start() Thomas Gleixner
2017-04-15 14:19   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 08/13] ACPI/processor: Replace racy task affinity logic Thomas Gleixner
2017-04-13 11:39   ` Peter Zijlstra
2017-04-13 12:01     ` Thomas Gleixner
2017-04-13 12:52       ` Peter Zijlstra
2017-04-15 14:19   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 09/13] cpufreq/ia64: " Thomas Gleixner
2017-04-12 20:55   ` [patch V2 " Thomas Gleixner
2017-04-15 14:20     ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-13  2:42   ` [patch 09/13] " Viresh Kumar
2017-04-12 20:07 ` [patch 10/13] cpufreq/sh: " Thomas Gleixner
2017-04-13  2:46   ` Viresh Kumar
2017-04-15 14:20   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 11/13] cpufreq/sparc-us3: " Thomas Gleixner
2017-04-13  2:48   ` Viresh Kumar
2017-04-15 14:21   ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-12 20:07 ` [patch 12/13] cpufreq/sparc-us2e: " Thomas Gleixner
2017-04-13  2:50   ` Viresh Kumar
2017-04-13  8:19   ` [patch V2 " Thomas Gleixner
2017-04-13  8:22     ` [patch V3 " Thomas Gleixner
2017-04-15 14:21       ` [tip:sched/core] " tip-bot for Thomas Gleixner
2017-04-13 14:50     ` [patch V2 12/13] " David Miller
2017-04-12 20:07 ` [patch 13/13] crypto: n2 - " Thomas Gleixner
2017-04-13  4:56   ` Herbert Xu
2017-04-13  8:20   ` [patch V2 " Thomas Gleixner
2017-04-13 14:51     ` David Miller
2017-04-15 14:22     ` [tip:sched/core] crypto: N2 " tip-bot for Thomas Gleixner
2017-04-13  9:02 ` [patch 00/13] sched/treewide: Clean up various racy task affinity issues Peter Zijlstra

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