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
......@@ -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 /* _LINUX_STOP_MACHINE */
#endif /* CONFIG_STOP_MACHINE && CONFIG_SMP */
#endif /* _LINUX_STOP_MACHINE */
......@@ -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
......
......@@ -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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