path: root/kernel/pid.c
diff options
authorPavel Emelyanov <>2012-01-12 17:20:27 -0800
committerLinus Torvalds <>2012-01-12 20:13:11 -0800
commitb8f566b04d3cddd192cfd2418ae6d54ac6353792 (patch)
tree32a5bf86548cd43feff4822d800b6a99e157b5d7 /kernel/pid.c
parentf5138e42211d4e8bfbd6ac5b3816348da1533433 (diff)
sysctl: add the kernel.ns_last_pid control
The sysctl works on the current task's pid namespace, getting and setting its last_pid field. Writing is allowed for CAP_SYS_ADMIN-capable tasks thus making it possible to create a task with desired pid value. This ability is required badly for the checkpoint/restore in userspace. This approach suits all the parties for now. Signed-off-by: Pavel Emelyanov <> Acked-by: Tejun Heo <> Cc: Oleg Nesterov <> Cc: Cyrill Gorcunov <> Cc: "Eric W. Biederman" <> Cc: Serge Hallyn <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel/pid.c')
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index fa5f72227e5f..ce8e00deaccb 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -137,7 +137,9 @@ static int pid_before(int base, int a, int b)
- * We might be racing with someone else trying to set pid_ns->last_pid.
+ * We might be racing with someone else trying to set pid_ns->last_pid
+ * at the pid allocation time (there's also a sysctl for this, but racing
+ * with this one is OK, see comment in kernel/pid_namespace.c about it).
* We want the winner to have the "later" value, because if the
* "earlier" value prevails, then a pid may get reused immediately.