That change looks correct to me, and I see that it's gone in.
It made me think of another issue affecting the accounting records in
related circumstances when the old group leader died after a non-leader exec.
I think this patch addresses that, and along with your patch, gives more
sensible times in all cases.
Thanks,
Roland
[PATCH] 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 <[email protected]>
---
fs/exec.c | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
7cda52efb6ff969f049bc2ab3742b0341e45184a
diff --git a/fs/exec.c b/fs/exec.c
index 0291a68..a45f712 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -678,6 +678,18 @@ static int de_thread(struct task_struct
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);
--
1.2.4
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