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Re: [PATCH] gdbserver: don't pick a random thread if the current thread dies

Pedro Alves wrote:

> 	* spu-low.c (spu_resume, spu_request_interrupt): Use the first
> 	thread's lwp instead of the current thread's.

>  static void
>  spu_request_interrupt (void)
>  {
> -  syscall (SYS_tkill, ptid_get_lwp (current_ptid), SIGINT);
> +  struct thread_info *thr = get_first_thread ();
> +
> +  syscall (SYS_tkill, ptid_get_lwp (thr), SIGINT);
>  }

This doesn't compile due to:

gdbserver/spu-low.c: In function 'spu_request_interrupt':
gdbserver/spu-low.c:639: error: incompatible type for argument 1 of 'ptid_get_lwp'

When adding the obvious fix ("ptid_of (thr)"), it does compile, but now
gdbserver crashes as soon as GDB attaches to it:

Program received signal SIGSEGV, Segmentation fault.                                                                                                                               
0x10008274 in read_ptid (buf=0x1005045a "0", obuf=0x0) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/remote-utils.c:578
578       pid = ptid_get_pid (current_ptid);
(gdb) bt
#0  0x10008274 in read_ptid (buf=0x1005045a "0", obuf=0x0) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/remote-utils.c:578
#1  0x1001045c in process_serial_event (err=<value optimized out>, client_data=<value optimized out>) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/server.c:3864
#2  handle_serial_event (err=<value optimized out>, client_data=<value optimized out>) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/server.c:4206
#3  0x100176c0 in handle_file_event (event_file_desc=<value optimized out>) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/event-loop.c:429
#4  0x10017e90 in process_event () at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/event-loop.c:184
#5  start_event_loop () at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/event-loop.c:547
#6  0x1000ce3c in captured_main (argc=3, argv=0x1) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/server.c:3559
#7  0x1000d370 in main (argc=3, argv=0xffbbf994) at /home/uweigand/fsf/binutils-gdb/gdb/gdbserver/server.c:3634
(gdb) list
573       /* No multi-process.  Just a tid.  */
574       tid = hex_or_minus_one (p, &pp);
576       /* Since the stub is not sending a process id, then default to
577          what's in the current inferior.  */
578       pid = ptid_get_pid (current_ptid);
580       if (obuf)
581         *obuf = pp;
582       return ptid_build (pid, tid, 0);

Looks like current_thread is NULL at this point.  Since this is generic
code, I'm not quite sure if this is a SPU-specific problem or not ...

Do you think this is related to your change?


  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain

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