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-rw-r--r--Documentation/cgroups/cgroups.txt20
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index c0358c30c64..fd588ff0e29 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -23,6 +23,7 @@ CONTENTS:
2.1 Basic Usage
2.2 Attaching processes
2.3 Mounting hierarchies by name
+ 2.4 Notification API
3. Kernel API
3.1 Overview
3.2 Synchronization
@@ -435,6 +436,25 @@ you give a subsystem a name.
The name of the subsystem appears as part of the hierarchy description
in /proc/mounts and /proc/<pid>/cgroups.
+2.4 Notification API
+--------------------
+
+There is mechanism which allows to get notifications about changing
+status of a cgroup.
+
+To register new notification handler you need:
+ - create a file descriptor for event notification using eventfd(2);
+ - open a control file to be monitored (e.g. memory.usage_in_bytes);
+ - write "<event_fd> <control_fd> <args>" to cgroup.event_control.
+ Interpretation of args is defined by control file implementation;
+
+eventfd will be woken up by control file implementation or when the
+cgroup is removed.
+
+To unregister notification handler just close eventfd.
+
+NOTE: Support of notifications should be implemented for the control
+file. See documentation for the subsystem.
3. Kernel API
=============