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authorBen Blum <bblum@andrew.cmu.edu>2011-05-26 16:25:20 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-26 17:12:34 -0700
commit74a1166dfe1135dcc168d35fa5261aa7e087011b (patch)
treea7add70f0344e2352b8d0d6beb10aef85c6585f7 /Documentation/cgroups
parentf780bdb7c1c73009cb57adcf99ef50027d80bf3c (diff)
downloadlwn-74a1166dfe1135dcc168d35fa5261aa7e087011b.tar.gz
lwn-74a1166dfe1135dcc168d35fa5261aa7e087011b.zip
cgroups: make procs file writable
Make procs file writable to move all threads by tgid at once. Add functionality that enables users to move all threads in a threadgroup at once to a cgroup by writing the tgid to the 'cgroup.procs' file. This current implementation makes use of a per-threadgroup rwsem that's taken for reading in the fork() path to prevent newly forking threads within the threadgroup from "escaping" while the move is in progress. Signed-off-by: Ben Blum <bblum@andrew.cmu.edu> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Matt Helsley <matthltc@us.ibm.com> Reviewed-by: Paul Menage <menage@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/cgroups')
-rw-r--r--Documentation/cgroups/cgroups.txt9
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index b3bd3bdbe202..8c4f3466c894 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -236,7 +236,8 @@ containing the following files describing that cgroup:
- cgroup.procs: list of tgids 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 is a read-only file, for now.
+ Writing a thread group id into this file moves all threads in that
+ group into this cgroup.
- notify_on_release flag: run the release agent on exit?
- release_agent: the path to use for release notifications (this file
exists in the top cgroup only)
@@ -430,6 +431,12 @@ You can attach the current shell task by echoing 0:
# echo 0 > tasks
+You can use the cgroup.procs file instead of the tasks file to move all
+threads in a threadgroup at once. Echoing the pid of any task in a
+threadgroup to cgroup.procs causes all tasks in that threadgroup to be
+be attached to the cgroup. Writing 0 to cgroup.procs moves all tasks
+in the writing task's threadgroup.
+
Note: Since every task is always a member of exactly one cgroup in each
mounted hierarchy, to remove a task from its current cgroup you must
move it into a new cgroup (possibly the root cgroup) by writing to the