Hello,
Currently, the pid list shown on cgroup->procs & tasks is in ascending order. However, this list is not
guaranteed to be sorted according to the following records mentioned at Documentation/cgroups/cgroups.txt.
- tasks: list of tasks (by PID) attached to that cgroup. This list
is not guaranteed to be sorted.
- cgroup.procs: list of thread group IDs in the cgroup. This list is
not guaranteed to be sorted or free of duplicate TGIDs, and userspace
should sort/uniquify the list if this property is required.
This patch remove the sorting function to make the default behavior of pid list be consistent with
the document.
Without patch:
# echo 2942 >> /cgroup/test/tasks
# echo 2803 >> /cgroup/test/tasks
# echo 2911 >> /cgroup/test/tasks
# echo 2761 >> /cgroup/test/tasks
# cat /cgroup/test/tasks
2761
2803
2911
2942
# cat /cgroup/test/cgroup.procs
2761
2803
2911
2942
Patch applied:
# echo 3042 >> /cgroup/testfixed/tasks
# echo 2916 >> /cgroup/testfixed/tasks
# echo 2781 >> /cgroup/testfixed/tasks
# echo 2527 >> /cgroup/testfixed/tasks
# cat /cgroup/testfixed/tasks
2916
3042
2527
2781
# cat /cgroup/testfixed/cgroup.procs
2916
3042
2527
2781
Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
---
kernel/cgroup.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f24f724..2b5b477 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -47,7 +47,6 @@
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
-#include <linux/sort.h>
#include <linux/kmod.h>
#include <linux/module.h>
#include <linux/delayacct.h>
@@ -3374,11 +3373,6 @@ after:
return dest;
}
-static int cmppid(const void *a, const void *b)
-{
- return *(pid_t *)a - *(pid_t *)b;
-}
-
/*
* find the appropriate pidlist for our purpose (given procs vs tasks)
* returns with the lock on that pidlist already held, and takes care
@@ -3463,8 +3457,7 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
}
cgroup_iter_end(cgrp, &it);
length = n;
- /* now sort & (if procs) strip out duplicates */
- sort(array, length, sizeof(pid_t), cmppid, NULL);
+ /* if procs, strip out duplicates */
if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(&array, length);
l = cgroup_pidlist_find(cgrp, type);
--
1.7.9.5
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