forked from Imagelibrary/binutils-gdb
3bc4e2059b
If GDB sets a GDB_TO_EXIT option on a thread, and the thread exits,
the server reports the corresponding thread exit event, and forgets
about the thread, i.e., removes the exited thread from its thread
list.
On the GDB side, GDB set the GDB_TO_EXIT option on a thread, GDB
delays deleting the thread from its thread list until it sees the
corresponding thread exit event, as that event needs special handling
in infrun.
When a thread disappears from the target, but it still exists on GDB's
thread list, in all-stop RSP mode, it can happen that GDB ends up
trying to resume such an already-exited-thread that GDB doesn't yet
know is gone. When that happens, against GDBserver, typically the
ongoing execution command fails with this error:
...
PC register is not available
(gdb)
At the remote protocol level, we may see e.g., this:
[remote] Packet received: w0;p97479.978d2
[remote] wait: exit
[infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) =
[infrun] print_target_wait_results: 619641.620754.0 [Thread 619641.620754],
[infrun] print_target_wait_results: status->kind = THREAD_EXITED, exit_status = 0
[infrun] handle_inferior_event: status->kind = THREAD_EXITED, exit_status = 0
[infrun] context_switch: Switching context from 0.0.0 to 619641.620754.0
[infrun] clear_proceed_status_thread: 619641.620754.0
GDB saw an exit event for thread 619641.620754. After processing it,
infrun decides to re-resume the target again. To do that, infrun
picks some other thread that isn't exited yet from GDB's perspective,
switches to it, and calls keep_going. Below, infrun happens to pick
thread p97479.97479, the leader, which also exited, but GDB doesn't
know yet:
...
[remote] Sending packet: $Hgp97479.97479#75
[remote] Packet received: OK
[remote] Sending packet: $g#67
[remote] Packet received: xxxxxxxxxxxxxxxxx (...snip...) [1120 bytes omitted]
[infrun] reset: reason=handling event
[infrun] maybe_set_commit_resumed_all_targets: not requesting commit-resumed for target remote, no resumed threads
[infrun] fetch_inferior_event: exit
PC register is not available
(gdb)
The Linux backends, both in GDB and in GDBserver, already silently
ignore failures to resume, with the understanding that we'll see an
exit event soon. Core of GDB doesn't do that yet, though.
This patch is a small step in that direction. It swallows the error
when thrown from within resume_1. There are likely are spots where we
will need similar treatment, but we can tackle them as we find them.
After this patch, we'll see something like this instead:
[infrun] resume_1: step=0, signal=GDB_SIGNAL_0, trap_expected=0, current thread [640478.640478.0] at 0x0
[infrun] do_target_resume: resume_ptid=640478.0.0, step=0, sig=GDB_SIGNAL_0
[remote] Sending packet: $vCont;c:p9c5de.-1#78
[infrun] prepare_to_wait: prepare_to_wait
[infrun] reset: reason=handling event
[infrun] maybe_set_commit_resumed_all_targets: enabling commit-resumed for target remote
[infrun] maybe_call_commit_resumed_all_targets: calling commit_resumed for target remote
[infrun] fetch_inferior_event: exit
[infrun] fetch_inferior_event: enter
[infrun] scoped_disable_commit_resumed: reason=handling event
[infrun] random_pending_event_thread: None found.
[remote] wait: enter
[remote] Packet received: W0;process:9c5de
[remote] wait: exit
[infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) =
[infrun] print_target_wait_results: 640478.0.0 [process 640478],
[infrun] print_target_wait_results: status->kind = EXITED, exit_status = 0
[infrun] handle_inferior_event: status->kind = EXITED, exit_status = 0
[Inferior 1 (process 640478) exited normally]
[infrun] stop_waiting: stop_waiting
[infrun] reset: reason=handling event
(gdb) [infrun] fetch_inferior_event: exit
Change-Id: I7f1c7610923435c4e98e70acc5ebe5ebbac581e2
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.