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[PATCH] pid: Implement transfer_pid and use it to simplify de_thread

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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>
This commit is contained in:
Eric W. Biederman 2006-09-27 01:51:06 -07:00 • committed by Linus Torvalds
parent 35fa2048ab
commit c18258c6f0
3 changed files with 15 additions and 7 deletions
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2
include/linux/pid.h
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@ -76,6 +76,8 @@ extern int FASTCALL(attach_pid(struct task_struct *task,
enum pid_type type, int nr));
extern void FASTCALL(detach_pid(struct task_struct *task, enum pid_type));
extern void FASTCALL(transfer_pid(struct task_struct *old,
struct task_struct *new, enum pid_type));
/*
* look up a PID in the hash table. Must be called with the tasklist_lock