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 <[EMAIL PROTECTED]> --- PT/include/linux/pid.h~2_do_each_pid_task 2007-10-25 16:22:12.000000000 +0400 +++ PT/include/linux/pid.h 2007-12-07 18:24:21.000000000 +0300 @@ -160,7 +160,13 @@ static inline pid_t pid_vnr(struct 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/