cpu_stop: implement stop_cpu[s]()
Implement a simplistic per-cpu maximum priority cpu monopolization
mechanism. A non-sleeping callback can be scheduled to run on one or
multiple cpus with maximum priority monopolozing those cpus. This is
primarily to replace and unify RT workqueue usage in stop_machine and
scheduler migration_thread which currently is serving multiple
purposes.
Four functions are provided - stop_one_cpu(), stop_one_cpu_nowait(),
stop_cpus() and try_stop_cpus().
This is to allow clean sharing of resources among stop_cpu and all the
migration thread users. One stopper thread per cpu is created which
is currently named "stopper/CPU". This will eventually replace the
migration thread and take on its name.
* This facility was originally named cpuhog and lived in separate
files but Peter Zijlstra nacked the name and thus got renamed to
cpu_stop and moved into stop_machine.c.
* Better reporting of preemption leak as per Peter's suggestion.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index baba3a2..efcbd6c 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -1,15 +1,46 @@
#ifndef _LINUX_STOP_MACHINE
#define _LINUX_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. */
+
#include <linux/cpu.h>
#include <linux/cpumask.h>
+#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
+ * function to be executed on a single or multiple cpus preempting all
+ * other processes and monopolizing those cpus until it finishes.
+ *
+ * Resources for this mechanism are preallocated when a cpu is brought
+ * up and requests are guaranteed to be served as long as the target
+ * cpus are online.
+ */
+
+typedef int (*cpu_stop_fn_t)(void *arg);
+
+struct cpu_stop_work {
+ struct list_head list; /* cpu_stopper->works */
+ cpu_stop_fn_t fn;
+ void *arg;
+ struct cpu_stop_done *done;
+};
+
+int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
+void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+ struct cpu_stop_work *work_buf);
+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);
+
+/*
+ * 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.
+ */
+
/**
* stop_machine: freeze the machine on all CPUs and run this function
* @fn: the function to run