On Sat, 13 Sep 2008 00:44:55 +0200, Pedro Alves wrote:
> On Friday 12 September 2008 23:12:27, Jan Kratochvil wrote:
> > various testcases - such as gdb.threads/bp_in_thread.exp - crash HEAD. 
> > Tested only on Fedora kernel-2.6.27-0.317.rc5.git10.fc10.x86_64 but I
> > expect it can happen anywhere.
> >
> > LINUX_HANDLE_EXTENDED_WAIT calls ADD_LWP but not ADD_THREAD.
> 
> Hmm, it may be due to something having changed in the scheduling, as I'm
> on ubuntu's 2.6.24-19-generic x86_64 SMP (dual core), and I never saw
> that happen.

Yes, the Fedora kernels have a different ptrace implementation (based on
utrace by Roland McGrath) which has more free but still permitted timing.


> Would it be possible to add the thread to the thread list, in
> addition to the lwp?

IMO the reason for two lists is that really these two resources are different.
You can perfectly have tracked LWPs with no corresponding thread structures.
Attached a testcase using clone(2) which if you CTRL-C it has a state:
(gdb) plist thread_list ptid
$1 = {pid = 25112, lwp = 25112, tid = 0}
(gdb) plist lwp_list ptid
$2 = {pid = 25112, lwp = 25115, tid = 0}
$3 = {pid = 25112, lwp = 25112, tid = 0}

New thread notification will come from libthread_db but some time in between
we have no corresponding thread structures such as they will never exist for
standalone LWPs.


Regards,
Jan