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authorPaul Jackson <pj@sgi.com>2008-02-07 00:14:46 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-07 08:42:22 -0800
commitc8d9c90c7ece28259436476a016cdecd25dccf2c (patch)
tree660e8ef2dec483afc399f6fdcdd4610d46f6796f /kernel/cpuset.c
parent2df167a300d7b3ab9949bbb02a8f604afd809b92 (diff)
downloadlinux-c8d9c90c7ece28259436476a016cdecd25dccf2c.tar.bz2
hotplug cpu: move tasks in empty cpusets to parent various other fixes
Various minor formatting and comment tweaks to Cliff Wickman's [PATCH_3_of_3]_cpusets__update_cpumask_revision.patch I had had "iff", meaning "if and only if" in a comment. However, except for ancient mathematicians, the abbreviation "iff" was a tad too cryptic. Cliff changed it to "if", presumably figuring that the "iff" was a typo. However, it was the "only if" half of the conjunction that was most interesting. Reword to emphasis the "only if" aspect. The locking comment for remove_tasks_in_empty_cpuset() was wrong; it said callback_mutex had to be held on entry. The opposite is true. Several mentions of attach_task() in comments needed to be changed to cgroup_attach_task(). A comment about notify_on_release was no longer relevant, as the line of code it had commented, namely: set_bit(CS_RELEASED_RESOURCE, &parent->flags); is no longer present in that place in the cpuset.c code. Similarly a comment about notify_on_release before the scan_for_empty_cpusets() routine was no longer relevant. Removed extra parentheses and unnecessary return statement. Renamed attach_task() to cpuset_attach() in various comments. Removed comment about not needing memory migration, as it seems the migration is done anyway, via the cpuset_attach() callback from cgroup_attach_task(). Signed-off-by: Paul Jackson <pj@sgi.com> Acked-by: Cliff Wickman <cpw@sgi.com> Cc: David Rientjes <rientjes@google.com> Cc: Paul Menage <menage@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cpuset.c')
-rw-r--r--kernel/cpuset.c41
1 files changed, 15 insertions, 26 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 918bee9dc7a2..6868c1e78917 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -752,7 +752,7 @@ static int update_cpumask(struct cpuset *cs, char *buf)
trialcs = *cs;
/*
- * An empty cpus_allowed is ok if there are no tasks in the cpuset.
+ * An empty cpus_allowed is ok only if the cpuset has no tasks.
* Since cpulist_parse() fails on an empty mask, we special case
* that parsing. The validate_change() call ensures that cpusets
* with tasks have cpus.
@@ -809,7 +809,7 @@ static int update_cpumask(struct cpuset *cs, char *buf)
* so that the migration code can allocate pages on these nodes.
*
* Call holding cgroup_mutex, so current's cpuset won't change
- * during this call, as cgroup_mutex holds off any attach_task()
+ * during this call, as manage_mutex holds off any cpuset_attach()
* calls. Therefore we don't need to take task_lock around the
* call to guarantee_online_mems(), as we know no one is changing
* our task's cpuset.
@@ -1661,8 +1661,8 @@ void cpuset_do_move_task(struct task_struct *tsk, struct cgroup_scanner *scan)
* @from: cpuset in which the tasks currently reside
* @to: cpuset to which the tasks will be moved
*
- * Called with manage_sem held
- * callback_mutex must not be held, as attach_task() will take it.
+ * Called with cgroup_mutex held
+ * callback_mutex must not be held, as cpuset_attach() will take it.
*
* The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
* calling callback functions for each.
@@ -1689,18 +1689,18 @@ static void move_member_tasks_to_cpuset(struct cpuset *from, struct cpuset *to)
* last CPU or node from a cpuset, then move the tasks in the empty
* cpuset to its next-highest non-empty parent.
*
- * The parent cpuset has some superset of the 'mems' nodes that the
- * newly empty cpuset held, so no migration of memory is necessary.
- *
- * Called with both manage_sem and callback_sem held
+ * Called with cgroup_mutex held
+ * callback_mutex must not be held, as cpuset_attach() will take it.
*/
static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
{
struct cpuset *parent;
- /* the cgroup's css_sets list is in use if there are tasks
- in the cpuset; the list is empty if there are none;
- the cs->css.refcnt seems always 0 */
+ /*
+ * The cgroup's css_sets list is in use if there are tasks
+ * in the cpuset; the list is empty if there are none;
+ * the cs->css.refcnt seems always 0.
+ */
if (list_empty(&cs->css.cgroup->css_sets))
return;
@@ -1709,14 +1709,8 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
* has online cpus, so can't be empty).
*/
parent = cs->parent;
- while (cpus_empty(parent->cpus_allowed)) {
- /*
- * this empty cpuset should now be considered to
- * have been used, and therefore eligible for
- * release when empty (if it is notify_on_release)
- */
+ while (cpus_empty(parent->cpus_allowed))
parent = parent->parent;
- }
move_member_tasks_to_cpuset(cs, parent);
}
@@ -1725,10 +1719,6 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
* Walk the specified cpuset subtree and look for empty cpusets.
* The tasks of such cpuset must be moved to a parent cpuset.
*
- * Note that such a notify_on_release cpuset must have had, at some time,
- * member tasks or cpuset descendants and cpus and memory, before it can
- * be a candidate for release.
- *
* Called with cgroup_mutex held. We take callback_mutex to modify
* cpus_allowed and mems_allowed.
*
@@ -1764,8 +1754,8 @@ static void scan_for_empty_cpusets(const struct cpuset *root)
cpus_and(cp->cpus_allowed, cp->cpus_allowed, cpu_online_map);
nodes_and(cp->mems_allowed, cp->mems_allowed,
node_states[N_HIGH_MEMORY]);
- if ((cpus_empty(cp->cpus_allowed) ||
- nodes_empty(cp->mems_allowed))) {
+ if (cpus_empty(cp->cpus_allowed) ||
+ nodes_empty(cp->mems_allowed)) {
/* Move tasks from the empty cpuset to a parent */
mutex_unlock(&callback_mutex);
remove_tasks_in_empty_cpuset(cp);
@@ -1773,7 +1763,6 @@ static void scan_for_empty_cpusets(const struct cpuset *root)
}
}
mutex_unlock(&callback_mutex);
- return;
}
/*
@@ -2207,7 +2196,7 @@ void __cpuset_memory_pressure_bump(void)
* - Used for /proc/<pid>/cpuset.
* - No need to task_lock(tsk) on this tsk->cpuset reference, as it
* doesn't really matter if tsk->cpuset changes after we read it,
- * and we take cgroup_mutex, keeping attach_task() from changing it
+ * and we take cgroup_mutex, keeping cpuset_attach() from changing it
* anyway.
*/
static int proc_cpuset_show(struct seq_file *m, void *unused_v)