Re: pthread_create does not return when remote debugging

Daniel Jacobowitz
2003-06-28T23:54:56Z

On Sat, Jun 28, 2003 at 06:33:53PM -0400, Jon Ringle wrote:
> On Saturday 28 June 2003 04:01 pm, Daniel Jacobowitz wrote:
> > On Sat, Jun 28, 2003 at 01:11:06PM -0400, Jon Ringle wrote:
> > > > > Could the problem be on the gdbserver side not sending back anything
> > > > > in response to gdb Sending packet: &c#63...Ack?
> > > >
> > > > No. That's a continue request. The target isn't stopping again, but
> > > > that's not gdbserver's fault... it won't respond to the client until
> > > > the program stops.
> > > >
> > > > Find out why it's not stopping...
> > >
> > > I turned on remote_debug = 1, and debug_threads = 1 on gdbserver, and I
> > > get the following on the target when I continue. The signal 32 looks
> > > suspect to me.
> >
> > It is correct. The thread manager uses that. What are you running on
> > the ARM board? What's the rest of the gdbserver log?
>
> The ARM board is running linux-2.2.16 w/ glibc-2.1.3. The arm-linux-gcc
> version is 2.95.2.

Gdbserver is issuing a single-step request. ARM doesn't have
single-step support in hardware, generally, so the kernel emulates it.
This behaviour almost certainly represents a problem with your kernel's
single-step implementation. One possible problem would be if your
compiler is using the "bx" instruction to return from functions; most
versions of the kernel can't single-step a bx instruction.

Here's a tweak to gdbserver which will prevent it from trying to
single-step in your case. Let me know if this works, please.

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer

2003-06-28 Daniel Jacobowitz <drow@mvista.com>

* linux-arm-low.c (arm_reinsert_addr): New function.
(the_low_target): Add arm_reinsert_addr.

Index: linux-arm-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/linux-arm-low.c,v
retrieving revision 1.5
diff -u -p -r1.5 linux-arm-low.c
--- linux-arm-low.c 18 Nov 2002 00:37:50 -0000 1.5
+++ linux-arm-low.c 28 Jun 2003 23:53:49 -0000
@@ -80,6 +80,17 @@ arm_breakpoint_at (CORE_ADDR where)
return 0;
}

+/* We only place breakpoints in empty marker functions, and thread locking
+ is outside of the function. So rather than importing software single-step,
+ we can just run until exit. */
+static CORE_ADDR
+arm_reinsert_addr ()
+{
+ unsigned long pc;
+ collect_register_by_name ("lr", &pc);
+ return pc;
+}
+
struct linux_target_ops the_low_target = {
arm_num_regs,
arm_regmap,
@@ -89,7 +100,7 @@ struct linux_target_ops the_low_target =
arm_set_pc,
(const char *) &arm_breakpoint,
arm_breakpoint_len,
- NULL,
+ arm_reinsert_addr,
0,
arm_breakpoint_at,
};