Subject: + ipc-document-general-ipc-locking-scheme.patch added to -mm tree
To: davidlohr.bueso@xxxxxx,manfred@xxxxxxxxxxxxxxxx,riel@xxxxxxxxxx,sedat.dilek@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 16 Jul 2013 15:51:55 -0700
The patch titled
Subject: ipc: document general ipc locking scheme
has been added to the -mm tree. Its filename is
ipc-document-general-ipc-locking-scheme.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipc-document-general-ipc-locking-scheme.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipc-document-general-ipc-locking-scheme.patch
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From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Subject: ipc: document general ipc locking scheme
As suggested by Andrew, add a generic initial locking scheme used
throughout all sysv ipc mechanisms. Documenting the ids rwsem, how rcu
can be enough to do the initial checks and when to actually acquire the
kern_ipc_perm.lock spinlock.
I found that adding it to util.c was generic enough.
Signed-off-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/util.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff -puN ipc/util.c~ipc-document-general-ipc-locking-scheme ipc/util.c
--- a/ipc/util.c~ipc-document-general-ipc-locking-scheme
+++ a/ipc/util.c
@@ -15,6 +15,14 @@
* Jun 2006 - namespaces ssupport
* OpenVZ, SWsoft Inc.
* Pavel Emelianov <xemul@xxxxxxxxxx>
+ *
+ * General sysv ipc locking scheme:
+ * when doing ipc id lookups, take the ids->rwsem
+ * rcu_read_lock()
+ * obtain the ipc object (kern_ipc_perm)
+ * perform security, capabilities, auditing and permission checks, etc.
+ * acquire the ipc lock (kern_ipc_perm.lock) throught ipc_lock_object()
+ * perform data updates (ie: SET, RMID, LOCK/UNLOCK commands)
*/
#include <linux/mm.h>
_
Patches currently in -mm which might be from davidlohr.bueso@xxxxxx are
linux-next.patch
ipcshm-introduce-lockless-functions-to-obtain-the-ipc-object.patch
ipcshm-shorten-critical-region-in-shmctl_down.patch
ipc-drop-ipcctl_pre_down.patch
ipc-drop-ipcctl_pre_down-fix.patch
ipcshm-introduce-shmctl_nolock.patch
ipcshm-make-shmctl_nolock-lockless.patch
ipcshm-shorten-critical-region-for-shmctl.patch
ipcshm-cleanup-do_shmat-pasta.patch
ipcshm-shorten-critical-region-for-shmat.patch
ipc-rename-ids-rw_mutex.patch
ipcmsg-drop-msg_unlock.patch
ipc-document-general-ipc-locking-scheme.patch
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