> Roland McGrath:
>
> o fix bogus ECHILD return from wait* with zombie group leader
>
> I'm not sure this is the fix, but it is possible indeed, given that the
> problem UML triggered was, IIRC, that when it exited, there wasn't a proper
> cleanup of the status, and the process became invisible but still kept a
> reference to the file in /tmp, preventing it from being deleted...
Yep, that makes sense. The race thing also explains why it doesn't
allways happen. I still can't reproduce it on my machine btw, so it's
hard for me to test whenever that really fixes it or not.
> I think you can search for it on linux.bkbits.net... I'll do that when I have
> time...
Attached below for reference.
Gerd
# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
# 2004/12/17 09:18:41-08:00 [EMAIL PROTECTED]
# [PATCH] fix bogus ECHILD return from wait* with zombie group leader
#
# Klaus Dittrich observed this bug and posted a test case for it.
#
# This patch fixes both that failure mode and some others possible. What
# Klaus saw was a false negative (i.e. ECHILD when there was a child)
# when the group leader was a zombie but delayed because other children
# live; in the test program this happens in a race between the two threads
# dying on a signal.
#
# The change to the TASK_TRACED case avoids a potential false positive
# (blocking, or WNOHANG returning 0, when there are really no children
# left), in the race condition where my_ptrace_child returns zero.
#
# Signed-off-by: Roland McGrath <[EMAIL PROTECTED]>
# Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
# Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
#
# kernel/exit.c
# 2004/12/17 00:09:08-08:00 [EMAIL PROTECTED] +13 -2
# fix bogus ECHILD return from wait* with zombie group leader
#
diff -Nru a/kernel/exit.c b/kernel/exit.c
--- a/kernel/exit.c 2005-01-10 14:00:38 +01:00
+++ b/kernel/exit.c 2005-01-10 14:00:38 +01:00
@@ -1319,6 +1319,10 @@
add_wait_queue(¤t->wait_chldexit,&wait);
repeat:
+ /*
+ * We will set this flag if we see any child that might later
+ * match our criteria, even if we are not able to reap it yet.
+ */
flag = 0;
current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock);
@@ -1337,11 +1341,14 @@
switch (p->state) {
case TASK_TRACED:
- flag = 1;
if (!my_ptrace_child(p))
continue;
/*FALLTHROUGH*/
case TASK_STOPPED:
+ /*
+ * It's stopped now, so it might later
+ * continue, exit, or stop again.
+ */
flag = 1;
if (!(options & WUNTRACED) &&
!my_ptrace_child(p))
@@ -1377,8 +1384,12 @@
goto end;
break;
}
- flag = 1;
check_continued:
+ /*
+ * It's running now, so it might later
+ * exit, stop, or stop and then continue.
+ */
+ flag = 1;
if (!unlikely(options & WCONTINUED))
continue;
retval = wait_task_continued(
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