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Subject[PATCH] cgroup, docs: add a note about returning EBUSY in some cases
Date
Explicitly document EBUSY returned by writing into cgroup.procs
if controllers are enabled; and writing into cgroup.subtree_control
if there are attached processes.

The return code might be slightly surprising, and because there is
nothing obviously better, let's document it at least.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
Cc: cgroups@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Documentation/cgroup-v2.txt | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index 74cdeaed9f7a..57302f88a4ad 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -799,6 +799,9 @@ All cgroup core files are prefixed with "cgroup."
When delegating a sub-hierarchy, write access to this file
should be granted along with the containing directory.

+ If the target cgroup has enabled controllers, writing to this
+ file will fail with EBUSY.
+
In a threaded cgroup, reading this file fails with EOPNOTSUPP
as all the processes belong to the thread root. Writing is
supported and moves every thread of the process to the cgroup.
@@ -850,6 +853,9 @@ All cgroup core files are prefixed with "cgroup."
the last one is effective. When multiple enable and disable
operations are specified, either all succeed or all fail.

+ If the cgroup has attached tasks, writing to this file will
+ fail with EBUSY.
+
cgroup.events
A read-only flat-keyed file which exists on non-root cgroups.
The following entries are defined. Unless specified
--
2.14.3
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