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authorRoland McGrath <roland@redhat.com>2006-04-11 09:54:16 +0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-11 17:18:42 +0400
commitf5e902817fee1589badca1284f49eecc0ef0c200 (patch)
treec72c0b9ae52c81ccecbd434fb886f8f668245f74
parent491d4bed8051c655c7664b85446e13901463eb63 (diff)
downloadlinux-f5e902817fee1589badca1284f49eecc0ef0c200.tar.xz
[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 <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--fs/exec.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 4d38ad0b70d6..3234a0c32d54 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(&current->proc_lock);
proc_dentry1 = proc_pid_unhash(current);