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Groups > linux.kernel > #1624112

[patch 14/20] kernel/hotplug: Use stop_machine_locked() in takedown_cpu()

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

takedown_cpu() is a cpu hotplug function invoking stop_machine(). The cpu
hotplug machinery holds the hotplug lock for write.

stop_machine() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.

Use stop_machine_locked() to avoid the nested call.

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

---
 kernel/cpu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -701,7 +701,7 @@ static int takedown_cpu(unsigned int cpu
 	/*
 	 * So now all preempt/rcu users must observe !cpu_active().
 	 */
-	err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
+	err = stop_machine_locked(take_cpu_down, NULL, cpumask_of(cpu));
 	if (err) {
 		/* CPU refused to die */
 		irq_unlock_sparse();

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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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