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stop_machine: Provide stop_machine_cpuslocked()
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_cpuslocked() 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> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20170524081547.400700852@linutronix.de
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2 changed files with 30 additions and 7 deletions
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@ -116,14 +116,28 @@ static inline int try_stop_cpus(const struct cpumask *cpumask,
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* @fn() runs.
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*
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* This can be thought of as a very heavy write lock, equivalent to
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* grabbing every spinlock in the kernel. */
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* grabbing every spinlock in the kernel.
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*
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* Protects against CPU hotplug.
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*/
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int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
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/**
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* stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
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* @fn: the function to run
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* @data: the data ptr for the @fn()
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* @cpus: the cpus to run the @fn() on (NULL = any online cpu)
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*
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* Same as above. Must be called from with in a cpus_read_lock() protected
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* region. Avoids nested calls to cpus_read_lock().
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*/
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int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
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int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
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const struct cpumask *cpus);
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#else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
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static inline int stop_machine(cpu_stop_fn_t fn, void *data,
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static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
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const struct cpumask *cpus)
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{
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unsigned long flags;
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@ -134,6 +148,12 @@ static inline int stop_machine(cpu_stop_fn_t fn, void *data,
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return ret;
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}
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static inline int stop_machine(cpu_stop_fn_t fn, void *data,
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const struct cpumask *cpus)
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{
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return stop_machine_cpuslocked(fn, data, cpus);
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}
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static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
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const struct cpumask *cpus)
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{
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@ -552,7 +552,8 @@ static int __init cpu_stop_init(void)
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}
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early_initcall(cpu_stop_init);
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static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
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int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
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const struct cpumask *cpus)
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{
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struct multi_stop_data msdata = {
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.fn = fn,
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@ -561,6 +562,8 @@ static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cp
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.active_cpus = cpus,
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};
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lockdep_assert_cpus_held();
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if (!stop_machine_initialized) {
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/*
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* Handle the case where stop_machine() is called
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@ -590,9 +593,9 @@ int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
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int ret;
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/* No CPUs can come up or down during this. */
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get_online_cpus();
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ret = __stop_machine(fn, data, cpus);
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put_online_cpus();
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cpus_read_lock();
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ret = stop_machine_cpuslocked(fn, data, cpus);
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cpus_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(stop_machine);
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