X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=kernel%2Fcpuset.c;h=50f5dc46368841de3497fe96534df12b871e530b;hb=a183561567b5446d3362b4839bd4f744f4b2af1e;hp=64ad59cfad9bc7c0d59e66616262c4dcc9c8608a;hpb=020958b6272882c1a8bfbe5f3e0927f3845c2698;p=linux-2.6-omap-h63xx.git

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 64ad59cfad9..50f5dc46368 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -38,6 +38,7 @@
 #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>
@@ -701,6 +702,36 @@ done:
 	/* Don't kfree(doms) -- partition_sched_domains() does that. */
 }
 
+static inline int started_after_time(struct task_struct *t1,
+				     struct timespec *time,
+				     struct task_struct *t2)
+{
+	int start_diff = timespec_compare(&t1->start_time, time);
+	if (start_diff > 0) {
+		return 1;
+	} else if (start_diff < 0) {
+		return 0;
+	} else {
+		/*
+		 * Arbitrarily, if two processes started at the same
+		 * time, we'll say that the lower pointer value
+		 * started first. Note that t2 may have exited by now
+		 * so this may not be a valid pointer any longer, but
+		 * that's fine - it still serves to distinguish
+		 * between two tasks started (effectively)
+		 * simultaneously.
+		 */
+		return t1 > t2;
+	}
+}
+
+static inline int started_after(void *p1, void *p2)
+{
+	struct task_struct *t1 = p1;
+	struct task_struct *t2 = p2;
+	return started_after_time(t1, &t2->start_time, t2);
+}
+
 /*
  * Call with manage_mutex held.  May take callback_mutex during call.
  */
@@ -708,8 +739,15 @@ done:
 static int update_cpumask(struct cpuset *cs, char *buf)
 {
 	struct cpuset trialcs;
-	int retval;
-	int cpus_changed, is_load_balanced;
+	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 ptr_heap heap;
+	struct timespec latest_time = { 0, 0 };
 
 	/* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */
 	if (cs == &top_cpuset)
@@ -736,14 +774,73 @@ static int update_cpumask(struct cpuset *cs, char *buf)
 	if (retval < 0)
 		return retval;
 
-	cpus_changed = !cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed);
+	/* 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;
+
 	is_load_balanced = is_sched_load_balance(&trialcs);
 
 	mutex_lock(&callback_mutex);
 	cs->cpus_allowed = trialcs.cpus_allowed;
 	mutex_unlock(&callback_mutex);
 
-	if (cpus_changed && is_load_balanced)
+ 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
+	 */
+	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;
+	}
+	heap_free(&heap);
+	if (is_load_balanced)
 		rebuild_sched_domains();
 
 	return 0;
@@ -1721,10 +1818,23 @@ cpumask_t cpuset_cpus_allowed(struct task_struct *tsk)
 	cpumask_t mask;
 
 	mutex_lock(&callback_mutex);
+	mask = cpuset_cpus_allowed_locked(tsk);
+	mutex_unlock(&callback_mutex);
+
+	return mask;
+}
+
+/**
+ * cpuset_cpus_allowed_locked - return cpus_allowed mask from a tasks cpuset.
+ * Must be  called with callback_mutex held.
+ **/
+cpumask_t cpuset_cpus_allowed_locked(struct task_struct *tsk)
+{
+	cpumask_t mask;
+
 	task_lock(tsk);
 	guarantee_online_cpus(task_cs(tsk), &mask);
 	task_unlock(tsk);
-	mutex_unlock(&callback_mutex);
 
 	return mask;
 }