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.

Tejun Heo committed 16 years ago

Commit bbf1bb31 parent fc390cd3 files · +68 −7Browse files

Unified · Split

3 files

include/linux/stop_machine.h +63 −6
kernel/Makefile +1 −1
kernel/stop_machine.c +4 −0

include/linux/stop_machine.h+63−6

@@ -6,8 +6,6 @@ · 5 unmodified lines
6	6	#include <linux/list.h>
7	7	#include <asm/system.h>
8	8
9		−#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
10		−
11	9	/*
12	10	* stop_cpu[s]() is simplistic per-cpu maximum priority cpu
13	11	* monopolization mechanism. The caller can specify a non-sleeping
@@ -18,9 +16,10 @@ · 4 unmodified lines
18	16	* up and requests are guaranteed to be served as long as the target
19	17	* cpus are online.
20	18	*/
21		−
22	19	typedef int (cpu_stop_fn_t)(void arg);
23	20
	21	+#ifdef CONFIG_SMP
	22	+
24	23	struct cpu_stop_work {
25	24	struct list_head list; /* cpu_stopper->works */
26	25	cpu_stop_fn_t fn;
@@ -34,12 +33,70 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, · 7 unmodified lines
34	33	int stop_cpus(const struct cpumask cpumask, cpu_stop_fn_t fn, void arg);
35	34	int try_stop_cpus(const struct cpumask cpumask, cpu_stop_fn_t fn, void arg);
36	35
	36	+#else /* CONFIG_SMP */
	37	+
	38	+#include <linux/workqueue.h>
	39	+
	40	+struct cpu_stop_work {
	41	+ struct work_struct work;
	42	+ cpu_stop_fn_t fn;
	43	+ void *arg;
	44	+};
	45	+
	46	+static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
	47	+{
	48	+ int ret = -ENOENT;
	49	+ preempt_disable();
	50	+ if (cpu == smp_processor_id())
	51	+ ret = fn(arg);
	52	+ preempt_enable();
	53	+ return ret;
	54	+}
	55	+
	56	+static void stop_one_cpu_nowait_workfn(struct work_struct *work)
	57	+{
	58	+ struct cpu_stop_work *stwork =
	59	+ container_of(work, struct cpu_stop_work, work);
	60	+ preempt_disable();
	61	+ stwork->fn(stwork->arg);
	62	+ preempt_enable();
	63	+}
	64	+
	65	+static inline void stop_one_cpu_nowait(unsigned int cpu,
	66	+ cpu_stop_fn_t fn, void *arg,
	67	+ struct cpu_stop_work *work_buf)
	68	+{
	69	+ if (cpu == smp_processor_id()) {
	70	+ INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
	71	+ work_buf->fn = fn;
	72	+ work_buf->arg = arg;
	73	+ schedule_work(&work_buf->work);
	74	+ }
	75	+}
	76	+
	77	+static inline int stop_cpus(const struct cpumask *cpumask,
	78	+ cpu_stop_fn_t fn, void *arg)
	79	+{
	80	+ if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
	81	+ return stop_one_cpu(raw_smp_processor_id(), fn, arg);
	82	+ return -ENOENT;
	83	+}
	84	+
	85	+static inline int try_stop_cpus(const struct cpumask *cpumask,
	86	+ cpu_stop_fn_t fn, void *arg)
	87	+{
	88	+ return stop_cpus(cpumask, fn, arg);
	89	+}
	90	+
	91	+#endif /* CONFIG_SMP */
	92	+
37	93	/*
38	94	* stop_machine "Bogolock": stop the entire machine, disable
39	95	* interrupts. This is a very heavy lock, which is equivalent to
40	96	* grabbing every spinlock (and more). So the "read" side to such a
41	97	* lock is anything which disables preeempt.
42	98	*/
	99	+#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
43	100
44	101	/**
45	102	* 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); · 21 unmodified lines
67	124	*/
68	125	int __stop_machine(int (fn)(void ), void data, const struct cpumask cpus);
69	126
70		−#else
	127	+#else /* CONFIG_STOP_MACHINE && CONFIG_SMP */
71	128
72	129	static inline int stop_machine(int (fn)(void ), void *data,
73	130	const struct cpumask *cpus)
@@ -79,5 +136,5 @@ static inline int stop_machine(int (fn)(void ), void *data, · 5 unmodified lines
79	136	return ret;
80	137	}
81	138
82		−#endif /* CONFIG_SMP */
83		−#endif /* _LINUX_STOP_MACHINE */
	139	+#endif /* CONFIG_STOP_MACHINE && CONFIG_SMP */
	140	+#endif /* _LINUX_STOP_MACHINE */

kernel/Makefile+1−1

@@ -68,7 +68,7 @@ obj-$(CONFIG_USER_NS) += user_namespace.o · 67 unmodified lines
68	68	obj-$(CONFIG_PID_NS) += pid_namespace.o
69	69	obj-$(CONFIG_IKCONFIG) += configs.o
70	70	obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o
71		−obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
	71	+obj-$(CONFIG_SMP) += stop_machine.o
72	72	obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
73	73	obj-$(CONFIG_AUDIT) += audit.o auditfilter.o audit_watch.o
74	74	obj-$(CONFIG_AUDITSYSCALL) += auditsc.o

kernel/stop_machine.c+4−0

@@ -375,6 +375,8 @@ static int __init cpu_stop_init(void) · 374 unmodified lines
375	375	}
376	376	early_initcall(cpu_stop_init);
377	377
	378	+#ifdef CONFIG_STOP_MACHINE
	379	+
378	380	/* This controls the threads on each CPU. */
379	381	enum stopmachine_state {
380	382	/* Dummy starting state for thread. */
@@ -477,3 +479,5 @@ int stop_machine(int (fn)(void ), void data, const struct cpumask cpus) · 96 unmodified lines
477	479	return ret;
478	480	}
479	481	EXPORT_SYMBOL_GPL(stop_machine);
	482	+
	483	+#endif /* CONFIG_STOP_MACHINE */

cpu_stop: add dummy implementation for UP

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