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Groups > linux.kernel > #1624103

[patch 02/20] stop_machine: Provide stop_machine_locked()

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject [patch 02/20] stop_machine: Provide stop_machine_locked()
Date 2017-04-15 19:40 +0200
Message-ID <twzPY-123-9@gated-at.bofh.it> (permalink)
References <twzPX-123-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Some call sites of stop_machine() are within a get_online_cpus() protected
region.

stop_machine() calls get_online_cpus() as well, which is possible in the
current implementation but prevents converting the hotplug locking to a
percpu rwsem.

Provide stop_machine_locked() to avoid nested calls to get_online_cpus().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 include/linux/stop_machine.h |   26 +++++++++++++++++++++++---
 kernel/stop_machine.c        |    4 ++--
 2 files changed, 25 insertions(+), 5 deletions(-)

--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -116,15 +116,29 @@ static inline int try_stop_cpus(const st
  * @fn() runs.
  *
  * This can be thought of as a very heavy write lock, equivalent to
- * grabbing every spinlock in the kernel. */
+ * grabbing every spinlock in the kernel.
+ *
+ * Protects against CPU hotplug.
+ */
 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 
+/**
+ * stop_machine_locked: freeze the machine on all CPUs and run this function
+ * @fn: the function to run
+ * @data: the data ptr for the @fn()
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
+ *
+ * Same as above. Must be called from with in a get_online_cpus() protected
+ * region. Avoids nested calls to get_online_cpus().
+ */
+int stop_machine_locked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
+
 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 				   const struct cpumask *cpus);
 #else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 
-static inline int stop_machine(cpu_stop_fn_t fn, void *data,
-				 const struct cpumask *cpus)
+static inline int stop_machine_locked(cpu_stop_fn_t fn, void *data,
+				      const struct cpumask *cpus)
 {
 	unsigned long flags;
 	int ret;
@@ -134,6 +148,12 @@ static inline int stop_machine(cpu_stop_
 	return ret;
 }
 
+static inline int stop_machine(cpu_stop_fn_t fn, void *data,
+			       const struct cpumask *cpus)
+{
+	return stop_machine_locked(fn, data, cpus);
+}
+
 static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 						 const struct cpumask *cpus)
 {
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -552,7 +552,7 @@ static int __init cpu_stop_init(void)
 }
 early_initcall(cpu_stop_init);
 
-static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
+int stop_machine_locked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
 {
 	struct multi_stop_data msdata = {
 		.fn = fn,
@@ -591,7 +591,7 @@ int stop_machine(cpu_stop_fn_t fn, void
 
 	/* No CPUs can come up or down during this. */
 	get_online_cpus();
-	ret = __stop_machine(fn, data, cpus);
+	ret = stop_machine_locked(fn, data, cpus);
 	put_online_cpus();
 	return ret;
 }

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Thread

[patch 00/20] cpu/hotplug: Convert get_online_cpus() to a percpu_rwsem Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 02/20] stop_machine: Provide stop_machine_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 20/20] cpu/hotplug: Convert hotplug locking to percpu rwsem Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
    Re: [patch 20/20] cpu/hotplug: Convert hotplug locking to percpu  rwsem Peter Zijlstra <peterz@infradead.org> - 2017-04-17 09:00 +0200
  [patch 17/20] PCI: Use cpu_hotplug_disable() instead of  get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
    Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of  get_online_cpus() Peter Zijlstra <peterz@infradead.org> - 2017-04-17 08:50 +0200
      Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of  get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-17 09:50 +0200
    Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of  get_online_cpus() Bjorn Helgaas <helgaas@kernel.org> - 2017-04-18 21:50 +0200
      Re: [patch 17/20] PCI: Use cpu_hotplug_disable() instead of  get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-18 22:00 +0200
  [patch 12/20] s390/kernel: Use stop_machine_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 13/20] powerpc/powernv: Use stop_machine_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 03/20] padata: Make padata_alloc() static Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
    Re: [patch 03/20] padata: Make padata_alloc() static "Jason A. Donenfeld" <Jason@zx2c4.com> - 2017-04-16 08:30 +0200
      Re: [patch 03/20] padata: Make padata_alloc() static Thomas Gleixner <tglx@linutronix.de> - 2017-04-17 11:20 +0200
  [patch 01/20] cpu/hotplug: Provide  cpuhp_setup/remove_state[_nocalls]_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 18/20] PCI: Replace the racy recursion prevention Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 04/20] padata: Avoid nested calls to get_online_cpus() in  pcrypt_init_padata() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 14/20] kernel/hotplug: Use stop_machine_locked() in  takedown_cpu() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 05/20] x86/mtrr: Remove get_online_cpus() from  mtrr_save_state() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 07/20] KVM/PPC/Book3S HV: Use  cpuhp_setup_state_nocalls_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 16/20] perf/x86/intel: Drop get_online_cpus() in  intel_snb_check_microcode() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
    Re: [patch 16/20] perf/x86/intel: Drop get_online_cpus() in  intel_snb_check_microcode() Borislav Petkov <bp@alien8.de> - 2017-04-18 13:30 +0200
  [patch 09/20] hwtracing/coresight-etm4x: Use  cpuhp_setup_state_nocalls_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 10/20] perf/x86/intel/cqm: Use cpuhp_setup_state_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
    Re: [patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked() "Rafael J. Wysocki" <rafael@kernel.org> - 2017-04-16 01:00 +0200
    Re: [patch 06/20] cpufreq: Use cpuhp_setup_state_nocalls_locked() Viresh Kumar <viresh.kumar@linaro.org> - 2017-04-17 06:20 +0200
  [patch 08/20] hwtracing/coresight-etm3x: Use the locked version of  cpuhp_setup_state_nocalls() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200
  [patch 11/20] ARM/hw_breakpoint: Use cpuhp_setup_state_locked() Thomas Gleixner <tglx@linutronix.de> - 2017-04-15 19:40 +0200

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