1 files changed, 22 insertions, 0 deletions

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 1c7fb0a94e28..704e474a93df 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -61,6 +61,7 @@ show up in /proc/sys/kernel:
 - rtsig-nr
 - sem
 - sg-big-buff                 [ generic SCSI device (sg) ]
+- shm_rmid_forced
 - shmall
 - shmmax                      [ sysv ipc ]
 - shmmni
@@ -518,6 +519,27 @@ kernel.  This value defaults to SHMMAX.
 
 ==============================================================
 
+shm_rmid_forced:
+
+Linux lets you set resource limits, including how much memory one
+process can consume, via setrlimit(2).  Unfortunately, shared memory
+segments are allowed to exist without association with any process, and
+thus might not be counted against any resource limits.  If enabled,
+shared memory segments are automatically destroyed when their attach
+count becomes zero after a detach or a process termination.  It will
+also destroy segments that were created, but never attached to, on exit
+from the process.  The only use left for IPC_RMID is to immediately
+destroy an unattached segment.  Of course, this breaks the way things are
+defined, so some applications might stop working.  Note that this
+feature will do you no good unless you also configure your resource
+limits (in particular, RLIMIT_AS and RLIMIT_NPROC).  Most systems don't
+need this.
+
+Note that if you change this from 0 to 1, already created segments
+without users and with a dead originative process will be destroyed.
+
+==============================================================
+
 softlockup_thresh:
 
 This value can be used to lower the softlockup tolerance threshold.  The