[PATCH 0/1] Was: utrace-cleanup branch

[Oleg Nesterov]

On 11/13, Oleg Nesterov wrote:
>
> Roland, I pulled the last changes in your tree (utrace-cleanup merged
> in utrace-ptrace) and did some testing.
>
> In short: utrace-ptrace does not work at all.
>
> It fails a lot (if not most) of tests, in particular
> sa-resethand-on-cont-signal hangs and clone-multi-ptrace silently
> crashes the kernel.
>
> The quick investigation didn't help, utrace.c has too much changes,
> I will read the code tomorrow from the very beginning.

Ooooooooooooohhhhhhhhh.

In short, the code in utrace.c was broken even before utrace-cleanup
was merged (but I bet utrace-cleanup adds more problems which I don't
understand yet), and the patch below "fixes" utrace.c (without
utrace-cleanup applied).

Cough. I guess you want to know why I didn't notice this before.
Because the code in my utrace.c didn't match the code in your
utrace-ptrace branch.

How did this happen? I added some hacks to utrace.c for debugging
purposes. In particular, I added the code to track engine alloc/free,
and added the dirty hack to fix "access_process_vm() under spinlock"
bug. And some more changes.

But! I do not remember how, why and when the code below was added to
utrace_attach_task() in my tree. I guess it was the temporary debugging
change which I forgot to revert later.

Will continue tomorrow.

Oleg.

--- OOPS/kernel/utrace.c~TTF	2009-11-15 03:48:09.000000000 +0100
+++ OOPS/kernel/utrace.c	2009-11-15 03:52:47.000000000 +0100
@@ -180,6 +180,10 @@ static int utrace_add_engine(struct task
 	 * notified about the event that precipitated its own
 	 * creation.  This is not what the user wants.
 	 */
+
+utrace->report = 1;
+set_notify_resume(target);
+
 	list_add_tail(&engine->entry, &utrace->attaching);
 	utrace->pending_attach = 1;
 	ret = 0;