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Re: [PATCH] gdbserver: don't pick a random thread if the current thread dies
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: palves at redhat dot com (Pedro Alves)
- Cc: gdb-patches at sourceware dot org
- Date: Mon, 24 Aug 2015 16:59:33 +0200 (CEST)
- Subject: Re: [PATCH] gdbserver: don't pick a random thread if the current thread dies
- Authentication-results: sourceware.org; auth=none
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);
575
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);
579
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?
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU/Linux compilers and toolchain
Ulrich.Weigand@de.ibm.com