From: Roland McGrath Date: Tue, 11 Apr 2006 05:54:16 +0000 (-0700) Subject: [PATCH] process accounting: take original leader's start_time in non-leader exec X-Git-Tag: v2.6.17-rc2~190 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f5e902817fee1589badca1284f49eecc0ef0c200;p=linux-2.6 [PATCH] process accounting: take original leader's start_time in non-leader exec The only record we have of the real-time age of a process, regardless of execs it's done, is start_time. When a non-leader thread exec, the original start_time of the process is lost. Things looking at the real-time age of the process are fooled, for example the process accounting record when the process finally dies. This change makes the oldest start_time stick around with the process after a non-leader exec. This way the association between PID and start_time is kept constant, which seems correct to me. Signed-off-by: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/exec.c b/fs/exec.c index 4d38ad0b70..3234a0c32d 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -678,6 +678,18 @@ static int de_thread(struct task_struct *tsk) while (leader->exit_state != EXIT_ZOMBIE) yield(); + /* + * The only record we have of the real-time age of a + * process, regardless of execs it's done, is start_time. + * All the past CPU time is accumulated in signal_struct + * from sister threads now dead. But in this non-leader + * exec, nothing survives from the original leader thread, + * whose birth marks the true age of this process now. + * When we take on its identity by switching to its PID, we + * also take its birthdate (always earlier than our own). + */ + current->start_time = leader->start_time; + spin_lock(&leader->proc_lock); spin_lock(¤t->proc_lock); proc_dentry1 = proc_pid_unhash(current);