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From: "tromey at sourceware dot org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/17626] New: attach, detach, attach did not work
Date: Wed, 19 Nov 2014 16:19:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=17626

            Bug ID: 17626
           Summary: attach, detach, attach did not work
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: tromey at sourceware dot org

I'm debugging firefox in "electrolysis" mode, where it
has two processes.  I used git gdb from a couple weeks ago.

First I attached to the parent process.  This went fine:

(gdb) attach 8126
Attaching to process 8126
Reading symbols from
/home/tromey/firefox-git/gecko-dev/obj-x86_64-unknown-linux-gnu/dist/bin/firefox...done.
[...lots more...]
0x00007facdb22c71d in poll () at ../sysdeps/unix/syscall-template.S:81


Now I detach immediately and try to attach to the child:

(gdb) detach
Detaching from program:
/home/tromey/firefox-git/gecko-dev/obj-x86_64-unknown-linux-gnu/dist/bin/firefox,
process 8126
[Inferior 8126 detached]
(gdb) attach 8189
Attaching to program:
/home/tromey/firefox-git/gecko-dev/obj-x86_64-unknown-linux-gnu/dist/bin/firefox,
process 8189
Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from
/usr/lib/debug/usr/lib64/ld-2.18.so.debug...done.
done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
0x00007f573f1f171d in ?? ()

gdb can't find the threads or do a stack trace:

(gdb) info thr
  Id   Target Id         Frame 
* 1    process 8189 "Web Content" 0x00007f573f1f171d in ?? ()
(gdb) bt
#0  0x00007f573f1f171d in ?? ()
#1  0x0000000000000000 in ?? ()


However, if I quit gdb and attach to the child, it works.

(gdb) attach 8189
Attaching to process 8189
Reading symbols from
/home/tromey/firefox-git/gecko-dev/obj-x86_64-unknown-linux-gnu/dist/bin/plugin-container...done.
[...lots more...]

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