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authorStanislav Kinsbursky <skinsbursky@parallels.com>2013-01-05 03:34:55 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-01-05 04:11:45 +0400
commit4a674f34ba04a002244edaf891b5da7fc1473ae8 (patch)
tree14544a5d49b4a218bac3f5995503c8e208735cef /include
parentf9dd87f4738c7555aca2cdf8cb2b2326cafb0cad (diff)
downloadlinux-4a674f34ba04a002244edaf891b5da7fc1473ae8.tar.xz
ipc: introduce message queue copy feature
This patch is required for checkpoint/restore in userspace. c/r requires some way to get all pending IPC messages without deleting them from the queue (checkpoint can fail and in this case tasks will be resumed, so queue have to be valid). To achive this, new operation flag MSG_COPY for sys_msgrcv() system call was introduced. If this flag was specified, then mtype is interpreted as number of the message to copy. If MSG_COPY is set, then kernel will allocate dummy message with passed size, and then use new copy_msg() helper function to copy desired message (instead of unlinking it from the queue). Notes: 1) Return -ENOSYS if MSG_COPY is specified, but CONFIG_CHECKPOINT_RESTORE is not set. Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com> Cc: Serge Hallyn <serge.hallyn@canonical.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/uapi/linux/msg.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/msg.h b/include/uapi/linux/msg.h
index 78dbd2f996a3..22d95c6854e0 100644
--- a/include/uapi/linux/msg.h
+++ b/include/uapi/linux/msg.h
@@ -10,6 +10,7 @@
/* msgrcv options */
#define MSG_NOERROR 010000 /* no error if message is too big */
#define MSG_EXCEPT 020000 /* recv any msg except of specified type.*/
+#define MSG_COPY 040000 /* copy (not remove) all queue messages */
/* Obsolete, used only for backwards compatibility and libc5 compiles */
struct msqid_ds {