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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-04-02 16:57:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-02 19:04:54 -0700
commitec64f51545fffbc4cb968f0cea56341a4b07e85a (patch)
tree575d890a6759d81f3324fa2a22ca6ab14a41eefc /Documentation/cgroups/cgroups.txt
parent38460b48d06440de46b34cb778bd6c4855030754 (diff)
cgroup: fix frequent -EBUSY at rmdir
In following situation, with memory subsystem, /groupA use_hierarchy==1 /01 some tasks /02 some tasks /03 some tasks /04 empty When tasks under 01/02/03 hit limit on /groupA, hierarchical reclaim is triggered and the kernel walks tree under groupA. In this case, rmdir /groupA/04 fails with -EBUSY frequently because of temporal refcnt from the kernel. In general. cgroup can be rmdir'd if there are no children groups and no tasks. Frequent fails of rmdir() is not useful to users. (And the reason for -EBUSY is unknown to users.....in most cases) This patch tries to modify above behavior, by - retries if css_refcnt is got by someone. - add "return value" to pre_destroy() and allows subsystem to say "we're really busy!" Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/cgroups/cgroups.txt')
-rw-r--r--Documentation/cgroups/cgroups.txt6
1 files changed, 4 insertions, 2 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 93feb8444489..cdc46a501b85 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -476,11 +476,13 @@ cgroup->parent is still valid. (Note - can also be called for a
newly-created cgroup if an error occurs after this subsystem's
create() method has been called for the new cgroup).
-void pre_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp);
+int pre_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp);
Called before checking the reference count on each subsystem. This may
be useful for subsystems which have some extra references even if
-there are not tasks in the cgroup.
+there are not tasks in the cgroup. If pre_destroy() returns error code,
+rmdir() will fail with it. From this behavior, pre_destroy() can be
+called multiple times against a cgroup.
int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task)