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authorEric W. Biederman <ebiederm@xmission.com>2006-09-27 01:51:06 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-27 08:26:19 -0700
commitc18258c6f0848f97e85287f6271c511a092bb784 (patch)
tree16c057a171b7623895ee208459392c1104193b84 /kernel/pid.c
parent35fa2048ab13d1be846be612e395c15c200bd51c (diff)
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[PATCH] pid: Implement transfer_pid and use it to simplify de_thread
In de_thread we move pids from one process to another, a rather ugly case. The function transfer_pid makes it clear what we are doing, and makes the action atomic. This is useful we ever want to atomically traverse the process group and session lists, in a rcu safe manner. Even if the atomic properties this change should be a win as transfer_pid should be less code to execute than executing both attach_pid and detach_pid, and this should make de_thread slightly smaller as only a single function call needs to be emitted. The only downside is that the code might be slower to execute as the odds are against transfer_pid being in cache. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/pid.c')
-rw-r--r--kernel/pid.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/pid.c b/kernel/pid.c
index 93e212f..6db82b6 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -252,6 +252,15 @@ void fastcall detach_pid(struct task_struct *task, enum pid_type type)
free_pid(pid);
}
+/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
+void fastcall transfer_pid(struct task_struct *old, struct task_struct *new,
+ enum pid_type type)
+{
+ new->pids[type].pid = old->pids[type].pid;
+ hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
+ old->pids[type].pid = NULL;
+}
+
struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type)
{
struct task_struct *result = NULL;