gdb/2250: Linux, multi-threaded, single-stepping, internal breakpoints

[emi-suzuki at tjsys dot co dot jp]

>Number:         2250
>Category:       gdb
>Synopsis:       Linux, multi-threaded, single-stepping, internal breakpoints
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 10 09:48:01 BST 2007
>Closed-Date:
>Last-Modified:
>Originator:     emi-suzuki@tjsys.co.jp
>Release:        GNU gdb 6.6.50.20070330-cvs
>Organization:
>Environment:
FC5 or 6 running on X86 or PPC64
built with GCC 4.1.0 or 4.1.1 (packaged in the disto)
>Description:
When the multi-threaded target get stopped by a internal breakpoint hit (ex. thread creation, thread death, shared library loading) during singe-stepping, GDB unconditionally resume all the thread and it result in running over the range of single-stepping.  
>How-To-Repeat:
The attached program makes two sub threads, and we do single-stepping on one of them.  

The session log below shows one of the phenomena reproduced on X86 FC6; the problem occured when the second thread was created.  

----
GNU gdb 6.6.50.20070330-cvs
Copyright (C) 2007 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i686-pc-linux-gnu"...
Using host libthread_db library "/lib/libthread_db.so.1".
(gdb) b 14
Breakpoint 1 at 0x80484fa: file mt.c, line 14.
(gdb) l 14
9       {
10        int i;
11        int cnt = *((int *) arg);
12        pid_t pid = getpid();
13
14        for (i=0; i<cnt; i++)
15          printf ("[%d]counter: %d\n", pid, i);
16
17        return NULL;
18      }
(gdb) r
Starting program: /project/07/user/suzuki/test/mt/mt
[Thread debugging using libthread_db enabled]
[New Thread -1208011072 (LWP 28472)]
[28472]start
[New Thread -1208013936 (LWP 28475)]
[Switching to Thread -1208013936 (LWP 28475)]

Breakpoint 1, counter (arg=0xbfd491b0) at mt.c:14
14        for (i=0; i<cnt; i++)
(gdb) s
[New Thread -1218503792 (LWP 28476)]
[28472]no_counter
[Thread -1218503792 (LWP 28476) exited]
[28472]counter: 0
[28472]counter: 1
[28472]counter: 2
[28472]counter: 3
[28472]counter: 4
[28472]counter: 5
[28472]counter: 6
[28472]counter: 7
[28472]counter: 8
[28472]counter: 9
[Thread -1208013936 (LWP 28475) exited]
Thread Event Breakpoint: gdb should not stop!
(gdb) 
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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