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uglify while_each_pid_task() to make sure we don't count the execing pricess twice

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There is a window when de_thread() switches the leader and drops
tasklist_lock.  In that window do_each_pid_task(PIDTYPE_PID) finds both new
and old leaders.

The problem is pretty much theoretical and probably can be ignored.  Currently
the only users of do_each_pid_task(PIDTYPE_PID) are send_sigio/send_sigurg, so
they can send the signal to the same process twice.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2008-02-08 04:19:19 -08:00 committed by Linus Torvalds
parent d36174bc2b
commit 46f382d2b6
1 changed files with 6 additions and 0 deletions
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6
include/linux/pid.h
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@ -152,7 +152,13 @@ pid_t pid_vnr(struct pid *pid);
hlist_for_each_entry_rcu((task), pos___, \
&pid->tasks[type], pids[type].node) {
/*
* Both old and new leaders may be attached to
* the same pid in the middle of de_thread().
*/
#define while_each_pid_task(pid, type, task) \
if (type == PIDTYPE_PID) \
break; \
} \
} while (0)