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Commit eeec4fad authored by Rusty Russell's avatar Rusty Russell
Browse files

stop_machine(): stop_machine_run() changed to use cpu mask 



Instead of a "cpu" arg with magic values NR_CPUS (any cpu) and ~0 (all
cpus), pass a cpumask_t.  Allow NULL for the common case (where we
don't care which CPU the function is run on): temporary cpumask_t's
are usually considered bad for stack space.

This deprecates stop_machine_run, to be removed soon when all the
callers are dead.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 04321587

include/linux/stop_machine.h

+24 −10
Original line number Diff line number Diff line
@@ -5,19 +5,19 @@ 
   (and more).  So the "read" side to such a lock is anything which

   diables preeempt. */

#include <linux/cpu.h>

#include <linux/cpumask.h>

#include <asm/system.h>



#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)



/* Deprecated, but useful for transition. */

#define ALL_CPUS ~0U



/**

 * stop_machine_run: freeze the machine on all CPUs and run this function

 * stop_machine: freeze the machine on all CPUs and run this function

 * @fn: the function to run

 * @data: the data ptr for the @fn()

 * @cpu: if @cpu == n, run @fn() on cpu n

 *       if @cpu == NR_CPUS, run @fn() on any cpu

 *       if @cpu == ALL_CPUS, run @fn() on every online CPU.

 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)

 *

 * Description: This causes a thread to be scheduled on every cpu,

 * each of which disables interrupts.  The result is that noone is
@@ -26,22 +26,22 @@ 
 *

 * This can be thought of as a very heavy write lock, equivalent to

 * grabbing every spinlock in the kernel. */

int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);

int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus);



/**

 * __stop_machine_run: freeze the machine on all CPUs and run this function

 * __stop_machine: freeze the machine on all CPUs and run this function

 * @fn: the function to run

 * @data: the data ptr for the @fn

 * @cpu: the cpu to run @fn on (or any, if @cpu == NR_CPUS.

 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)

 *

 * Description: This is a special version of the above, which assumes cpus

 * won't come or go while it's being called.  Used by hotplug cpu.

 */

int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu);

int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus);

#else



static inline int stop_machine_run(int (*fn)(void *), void *data,

				   unsigned int cpu)

static inline int stop_machine(int (*fn)(void *), void *data,

			       const cpumask_t *cpus)

{

	int ret;

	local_irq_disable();
@@ -50,4 +50,18 @@ static inline int stop_machine_run(int (*fn)(void *), void *data, 
	return ret;

}

#endif /* CONFIG_SMP */



static inline int __deprecated stop_machine_run(int (*fn)(void *), void *data,

						unsigned int cpu)

{

	/* If they don't care which cpu fn runs on, just pick one. */

	if (cpu == NR_CPUS)

		return stop_machine(fn, data, NULL);

	else if (cpu == ~0U)

		return stop_machine(fn, data, &cpu_possible_map);

	else {

		cpumask_t cpus = cpumask_of_cpu(cpu);

		return stop_machine(fn, data, &cpus);

	}

}

#endif /* _LINUX_STOP_MACHINE */

kernel/cpu.c

+2 −1
Original line number Diff line number Diff line
@@ -248,8 +248,9 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 
	cpus_setall(tmp);

	cpu_clear(cpu, tmp);

	set_cpus_allowed_ptr(current, &tmp);

	tmp = cpumask_of_cpu(cpu);



	err = __stop_machine_run(take_cpu_down, &tcd_param, cpu);

	err = __stop_machine(take_cpu_down, &tcd_param, &tmp);

	if (err) {

		/* CPU didn't die: tell everyone.  Can't complain. */

		if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,

kernel/stop_machine.c

+13 −14
Original line number Diff line number Diff line
@@ -100,7 +100,7 @@ static int chill(void *unused) 
	return 0;

}



int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)

int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)

{

	int i, err;

	struct stop_machine_data active, idle;
@@ -112,10 +112,6 @@ int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) 
	idle.fn = chill;

	idle.data = NULL;



	/* If they don't care which cpu fn runs on, just pick one. */

	if (cpu == NR_CPUS)

		cpu = any_online_cpu(cpu_online_map);



	/* This could be too big for stack on large machines. */

	threads = kcalloc(NR_CPUS, sizeof(threads[0]), GFP_KERNEL);

	if (!threads)
@@ -128,13 +124,16 @@ int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) 
	set_state(STOPMACHINE_PREPARE);



	for_each_online_cpu(i) {

		struct stop_machine_data *smdata;

		struct stop_machine_data *smdata = &idle;

		struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };



		if (cpu == ALL_CPUS || i == cpu)

		if (!cpus) {

			if (i == first_cpu(cpu_online_map))

				smdata = &active;

		else

			smdata = &idle;

		} else {

			if (cpu_isset(i, *cpus))

				smdata = &active;

		}



		threads[i] = kthread_create((void *)stop_cpu, smdata, "kstop%u",

					    i);
@@ -154,7 +153,7 @@ int __stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) 


	/* We've created all the threads.  Wake them all: hold this CPU so one

	 * doesn't hit this CPU until we're ready. */

	cpu = get_cpu();

	get_cpu();

	for_each_online_cpu(i)

		wake_up_process(threads[i]);
@@ -177,15 +176,15 @@ kill_threads: 
	return err;

}



int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)

int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)

{

	int ret;



	/* No CPUs can come up or down during this. */

	get_online_cpus();

	ret = __stop_machine_run(fn, data, cpu);

	ret = __stop_machine(fn, data, cpus);

	put_online_cpus();



	return ret;

}

EXPORT_SYMBOL_GPL(stop_machine_run);
 
EXPORT_SYMBOL_GPL(stop_machine);