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authorPaul Menage <menage@google.com>2008-10-18 20:28:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-20 08:52:38 -0700
commitcc31edceee04a7b87f2be48f9489ebb72d264844 (patch)
tree5d37791218c420281e509899645d89aee7902f2b /include/linux/cgroup.h
parent146aa1bd0511f88ddb4e92fafa2b8aad4f2f65f3 (diff)
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cgroups: convert tasks file to use a seq_file with shared pid array
Rather than pre-generating the entire text for the "tasks" file each time the file is opened, we instead just generate/update the array of process ids and use a seq_file to report these to userspace. All open file handles on the same "tasks" file can share a pid array, which may be updated any time that no thread is actively reading the array. By sharing the array, the potential for userspace to DoS the system by opening many handles on the same "tasks" file is removed. [Based on a patch by Lai Jiangshan, extended to use seq_file] Signed-off-by: Paul Menage <menage@google.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Serge Hallyn <serue@us.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/cgroup.h')
-rw-r--r--include/linux/cgroup.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 7166023..8ab9188 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -14,6 +14,7 @@
#include <linux/rcupdate.h>
#include <linux/cgroupstats.h>
#include <linux/prio_heap.h>
+#include <linux/rwsem.h>
#ifdef CONFIG_CGROUPS
@@ -136,6 +137,15 @@ struct cgroup {
* release_list_lock
*/
struct list_head release_list;
+
+ /* pids_mutex protects the fields below */
+ struct rw_semaphore pids_mutex;
+ /* Array of process ids in the cgroup */
+ pid_t *tasks_pids;
+ /* How many files are using the current tasks_pids array */
+ int pids_use_count;
+ /* Length of the current tasks_pids array */
+ int pids_length;
};
/* A css_set is a structure holding pointers to a set of