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[PATCH] process accounting: take original leader's start_time in non-leader exec

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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 <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Roland McGrath 2006-04-10 22:54:16 -07:00 committed by Linus Torvalds
parent 491d4bed80
commit f5e902817f
1 changed files with 12 additions and 0 deletions
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12
fs/exec.c
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@ -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(&current->proc_lock);
proc_dentry1 = proc_pid_unhash(current);