Commit bbf1bb3e authored by Tejun Heo's avatar Tejun Heo
Browse files

cpu_stop: add dummy implementation for UP 



When !CONFIG_SMP, cpu_stop functions weren't defined at all which
could lead to build failures if UP code uses cpu_stop facility.  Add
dummy cpu_stop implementation for UP.  The waiting variants execute
the work function directly with preempt disabled and
stop_one_cpu_nowait() schedules a workqueue work.

Makefile and ifdefs around stop_machine implementation are updated to
accomodate CONFIG_SMP && !CONFIG_STOP_MACHINE case.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarIngo Molnar <mingo@elte.hu>
parent fc390cde

include/linux/stop_machine.h

+63 −6
Original line number Diff line number Diff line
@@ -6,8 +6,6 @@ 
#include <linux/list.h>

#include <asm/system.h>



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



/*

 * stop_cpu[s]() is simplistic per-cpu maximum priority cpu

 * monopolization mechanism.  The caller can specify a non-sleeping
@@ -18,9 +16,10 @@ 
 * up and requests are guaranteed to be served as long as the target

 * cpus are online.

 */



typedef int (*cpu_stop_fn_t)(void *arg);



#ifdef CONFIG_SMP



struct cpu_stop_work {

	struct list_head	list;		/* cpu_stopper->works */

	cpu_stop_fn_t		fn;
@@ -34,12 +33,70 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, 
int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);

int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);



#else	/* CONFIG_SMP */



#include <linux/workqueue.h>



struct cpu_stop_work {

	struct work_struct	work;

	cpu_stop_fn_t		fn;

	void			*arg;

};



static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)

{

	int ret = -ENOENT;

	preempt_disable();

	if (cpu == smp_processor_id())

		ret = fn(arg);

	preempt_enable();

	return ret;

}



static void stop_one_cpu_nowait_workfn(struct work_struct *work)

{

	struct cpu_stop_work *stwork =

		container_of(work, struct cpu_stop_work, work);

	preempt_disable();

	stwork->fn(stwork->arg);

	preempt_enable();

}



static inline void stop_one_cpu_nowait(unsigned int cpu,

				       cpu_stop_fn_t fn, void *arg,

				       struct cpu_stop_work *work_buf)

{

	if (cpu == smp_processor_id()) {

		INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);

		work_buf->fn = fn;

		work_buf->arg = arg;

		schedule_work(&work_buf->work);

	}

}



static inline int stop_cpus(const struct cpumask *cpumask,

			    cpu_stop_fn_t fn, void *arg)

{

	if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))

		return stop_one_cpu(raw_smp_processor_id(), fn, arg);

	return -ENOENT;

}



static inline int try_stop_cpus(const struct cpumask *cpumask,

				cpu_stop_fn_t fn, void *arg)

{

	return stop_cpus(cpumask, fn, arg);

}



#endif	/* CONFIG_SMP */



/*

 * stop_machine "Bogolock": stop the entire machine, disable

 * interrupts.  This is a very heavy lock, which is equivalent to

 * grabbing every spinlock (and more).  So the "read" side to such a

 * lock is anything which disables preeempt.

 */

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



/**

 * stop_machine: freeze the machine on all CPUs and run this function
@@ -67,7 +124,7 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus); 
 */

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



#else

#else	 /* CONFIG_STOP_MACHINE && CONFIG_SMP */



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

			       const struct cpumask *cpus)
@@ -79,5 +136,5 @@ static inline int stop_machine(int (*fn)(void *), void *data, 
	return ret;

}



#endif /* CONFIG_SMP */

#endif	/* CONFIG_STOP_MACHINE && CONFIG_SMP */

#endif	/* _LINUX_STOP_MACHINE */

kernel/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -68,7 +68,7 @@ obj-$(CONFIG_USER_NS) += user_namespace.o 
obj-$(CONFIG_PID_NS) += pid_namespace.o

obj-$(CONFIG_IKCONFIG) += configs.o

obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o

obj-$(CONFIG_STOP_MACHINE) += stop_machine.o

obj-$(CONFIG_SMP) += stop_machine.o

obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o

obj-$(CONFIG_AUDIT) += audit.o auditfilter.o audit_watch.o

obj-$(CONFIG_AUDITSYSCALL) += auditsc.o

kernel/stop_machine.c

+4 −0
Original line number Diff line number Diff line
@@ -375,6 +375,8 @@ static int __init cpu_stop_init(void) 
}

early_initcall(cpu_stop_init);



#ifdef CONFIG_STOP_MACHINE



/* This controls the threads on each CPU. */

enum stopmachine_state {

	/* Dummy starting state for thread. */
@@ -477,3 +479,5 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) 
	return ret;

}

EXPORT_SYMBOL_GPL(stop_machine);



#endif	/* CONFIG_STOP_MACHINE */

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