cpusets: update_cpumask revision
Use the new function cgroup_scan_tasks() to step through all tasks in a
cpuset.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Cliff Wickman <cpw@sgi.com>
Cc: Paul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index d94a8f7..20cb391 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -38,7 +38,6 @@
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
-#include <linux/prio_heap.h>
#include <linux/proc_fs.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
@@ -740,22 +739,50 @@
return started_after_time(t1, &t2->start_time, t2);
}
-/*
+/**
+ * cpuset_test_cpumask - test a task's cpus_allowed versus its cpuset's
+ * @tsk: task to test
+ * @scan: struct cgroup_scanner contained in its struct cpuset_hotplug_scanner
+ *
* Call with manage_mutex held. May take callback_mutex during call.
+ * Called for each task in a cgroup by cgroup_scan_tasks().
+ * Return nonzero if this tasks's cpus_allowed mask should be changed (in other
+ * words, if its mask is not equal to its cpuset's mask).
*/
+int cpuset_test_cpumask(struct task_struct *tsk, struct cgroup_scanner *scan)
+{
+ return !cpus_equal(tsk->cpus_allowed,
+ (cgroup_cs(scan->cg))->cpus_allowed);
+}
+/**
+ * cpuset_change_cpumask - make a task's cpus_allowed the same as its cpuset's
+ * @tsk: task to test
+ * @scan: struct cgroup_scanner containing the cgroup of the task
+ *
+ * Called by cgroup_scan_tasks() for each task in a cgroup whose
+ * cpus_allowed mask needs to be changed.
+ *
+ * We don't need to re-check for the cgroup/cpuset membership, since we're
+ * holding cgroup_lock() at this point.
+ */
+void cpuset_change_cpumask(struct task_struct *tsk, struct cgroup_scanner *scan)
+{
+ set_cpus_allowed(tsk, (cgroup_cs(scan->cg))->cpus_allowed);
+}
+
+/**
+ * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
+ * @cs: the cpuset to consider
+ * @buf: buffer of cpu numbers written to this cpuset
+ */
static int update_cpumask(struct cpuset *cs, char *buf)
{
struct cpuset trialcs;
- int retval, i;
- int is_load_balanced;
- struct cgroup_iter it;
- struct cgroup *cgrp = cs->css.cgroup;
- struct task_struct *p, *dropped;
- /* Never dereference latest_task, since it's not refcounted */
- struct task_struct *latest_task = NULL;
+ struct cgroup_scanner scan;
struct ptr_heap heap;
- struct timespec latest_time = { 0, 0 };
+ int retval;
+ int is_load_balanced;
/* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */
if (cs == &top_cpuset)
@@ -764,7 +791,7 @@
trialcs = *cs;
/*
- * An empty cpus_allowed is ok iff there are no tasks in the cpuset.
+ * An empty cpus_allowed is ok if there are no tasks in the cpuset.
* Since cpulist_parse() fails on an empty mask, we special case
* that parsing. The validate_change() call ensures that cpusets
* with tasks have cpus.
@@ -785,6 +812,7 @@
/* Nothing to do if the cpus didn't change */
if (cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed))
return 0;
+
retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, &started_after);
if (retval)
return retval;
@@ -795,62 +823,19 @@
cs->cpus_allowed = trialcs.cpus_allowed;
mutex_unlock(&callback_mutex);
- again:
/*
* Scan tasks in the cpuset, and update the cpumasks of any
- * that need an update. Since we can't call set_cpus_allowed()
- * while holding tasklist_lock, gather tasks to be processed
- * in a heap structure. If the statically-sized heap fills up,
- * overflow tasks that started later, and in future iterations
- * only consider tasks that started after the latest task in
- * the previous pass. This guarantees forward progress and
- * that we don't miss any tasks
+ * that need an update.
*/
- heap.size = 0;
- cgroup_iter_start(cgrp, &it);
- while ((p = cgroup_iter_next(cgrp, &it))) {
- /* Only affect tasks that don't have the right cpus_allowed */
- if (cpus_equal(p->cpus_allowed, cs->cpus_allowed))
- continue;
- /*
- * Only process tasks that started after the last task
- * we processed
- */
- if (!started_after_time(p, &latest_time, latest_task))
- continue;
- dropped = heap_insert(&heap, p);
- if (dropped == NULL) {
- get_task_struct(p);
- } else if (dropped != p) {
- get_task_struct(p);
- put_task_struct(dropped);
- }
- }
- cgroup_iter_end(cgrp, &it);
- if (heap.size) {
- for (i = 0; i < heap.size; i++) {
- struct task_struct *p = heap.ptrs[i];
- if (i == 0) {
- latest_time = p->start_time;
- latest_task = p;
- }
- set_cpus_allowed(p, cs->cpus_allowed);
- put_task_struct(p);
- }
- /*
- * If we had to process any tasks at all, scan again
- * in case some of them were in the middle of forking
- * children that didn't notice the new cpumask
- * restriction. Not the most efficient way to do it,
- * but it avoids having to take callback_mutex in the
- * fork path
- */
- goto again;
- }
+ scan.cg = cs->css.cgroup;
+ scan.test_task = cpuset_test_cpumask;
+ scan.process_task = cpuset_change_cpumask;
+ scan.heap = &heap;
+ cgroup_scan_tasks(&scan);
heap_free(&heap);
+
if (is_load_balanced)
rebuild_sched_domains();
-
return 0;
}