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RE: debug of multithreaded program turns to be impossible during execution
- From: Avi Gozlan <avi at checkpoint dot com>
- To: Pedro Alves <palves at redhat dot com>, "gdb at sourceware dot org" <gdb at sourceware dot org>
- Cc: Avi Gozlan <avi at checkpoint dot com>
- Date: Thu, 14 Aug 2014 15:52:40 +0000
- Subject: RE: debug of multithreaded program turns to be impossible during execution
- Authentication-results: sourceware.org; auth=none
- References: <71C49BB0B847984EAADFE43F93C6BF083ADA7BE0 at DAG-EX10 dot ad dot checkpoint dot com> <53DA17B5 dot 10703 at redhat dot com>
GDB 7.8 yields a similar behavior:
[New Thread 0x43c05940 (LWP 3311)]
[New Thread 0x44606940 (LWP 3312)]
[Thread 0x44606940 (LWP 3312) exited]
[Switching to Thread 0x43c05940 (LWP 3311)]
Cannot remove breakpoints because program is no longer writable.
Further execution is probably impossible.
0x00002aaaab98348f in start_thread () from /lib64/libpthread.so.0
ptrace: No such process.
(gdb) [Thread 0x46409940 (LWP 3315) exited]
[Thread 0x45a08940 (LWP 3314) exited]
[Thread 0x43c05940 (LWP 3311) exited]
[Inferior 1 (process 3268) exited normally]
The only difference is that in 7.8 case, GDB continues automatically after giving the ptrace message.
From: Pedro Alves [mailto:email@example.com]
Sent: Thursday, July 31, 2014 1:17 PM
To: Avi Gozlan; firstname.lastname@example.org
Subject: Re: debug of multithreaded program turns to be impossible during execution
On 07/31/2014 10:27 AM, Avi Gozlan wrote:
> I'm debugging a multithreaded program using GDB. Various threads are created and exit during execution. GDB copes successfully with the multiple threads (e.g. 'thread apply 3 bt' reports successfully backtrace of thread 3), but then at one point loses control of the program:
> (gdb) c
> [New Thread 0x41401940 (LWP 13370)]
> [Thread 0x40a00940 (LWP 13333) exited] [New Thread 0x41e02940 (LWP
> 13371)] ...
> [New Thread 0x45a08940 (LWP 13377)]
> [New Thread 0x46409940 (LWP 13378)]
> [Thread 0x41e02940 (LWP 13371) exited] [Switching to Thread
> 0x45a08940 (LWP 13377)] Cannot remove breakpoints because program is
> no longer writable.
> Further execution is probably impossible.
> 0x00002aaaab98348f in start_thread () from /lib64/libpthread.so.0
> ptrace: No such process.
> Surprisingly, although debugging is no more possible, the program is not dead:
I have a vague recollection that this was fixed a while ago. Like, GDB was picking the wrong thread to access memory, and it ended up picking a running or exited thread, and that fails (in either case ptrace complains the same say).
> GDB version: 7.6
Is there a chance you could try a more recent GDB version? Ideally 7.8, which we just released.
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