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stop_machine: Provide stop_machine_cpuslocked()

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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
This commit is contained in:
Sebastian Andrzej Siewior 2017-05-24 10:15:16 +02:00 committed by Thomas Gleixner
parent 9805c67333
commit fe5595c074
2 changed files with 30 additions and 7 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

26
include/linux/stop_machine.h
View file

@ -116,15 +116,29 @@ static inline int try_stop_cpus(const struct cpumask *cpumask,
* @fn() runs. * @fn() runs.
* *
* This can be thought of as a very heavy write lock, equivalent to * 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); int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
/**
* stop_machine_cpuslocked: 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 cpus_read_lock() protected
* region. Avoids nested calls to cpus_read_lock().
*/
int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
const struct cpumask *cpus); const struct cpumask *cpus);
#else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */ #else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
static inline int stop_machine(cpu_stop_fn_t fn, void *data, static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
const struct cpumask *cpus) const struct cpumask *cpus)
{ {
unsigned long flags; unsigned long flags;
int ret; int ret;
@ -134,6 +148,12 @@ static inline int stop_machine(cpu_stop_fn_t fn, void *data,
return ret; return ret;
} }
static inline int stop_machine(cpu_stop_fn_t fn, void *data,
const struct cpumask *cpus)
{
return stop_machine_cpuslocked(fn, data, cpus);
}
static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
const struct cpumask *cpus) const struct cpumask *cpus)
{ {

11
kernel/stop_machine.c
View file

@ -552,7 +552,8 @@ static int __init cpu_stop_init(void)
} }
early_initcall(cpu_stop_init); early_initcall(cpu_stop_init);
static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus) int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
const struct cpumask *cpus)
{ {
struct multi_stop_data msdata = { struct multi_stop_data msdata = {
.fn = fn, .fn = fn,
@ -561,6 +562,8 @@ static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cp
.active_cpus = cpus, .active_cpus = cpus,
}; };
lockdep_assert_cpus_held();
if (!stop_machine_initialized) { if (!stop_machine_initialized) {
/* /*
* Handle the case where stop_machine() is called * Handle the case where stop_machine() is called
@ -590,9 +593,9 @@ int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
int ret; int ret;
/* No CPUs can come up or down during this. */ /* No CPUs can come up or down during this. */
get_online_cpus(); cpus_read_lock();
ret = __stop_machine(fn, data, cpus); ret = stop_machine_cpuslocked(fn, data, cpus);
put_online_cpus(); cpus_read_unlock();
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(stop_machine); EXPORT_SYMBOL_GPL(stop_machine);