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f0881b37b6
We have places where we call a blocking gdb_select expecting that a
Ctrl-C will unblock it. However, if the Ctrl-C is pressed just before
gdb_select, the SIGINT handler runs before gdb_select, and thus
gdb_select won't return.
For example gdb_readline_no_editing:
QUIT;
/* Wait until at least one byte of data is available. Control-C
can interrupt gdb_select, but not fgetc. */
FD_ZERO (&readfds);
FD_SET (fd, &readfds);
if (gdb_select (fd + 1, &readfds, NULL, NULL, NULL) == -1)
and stdio_file_read:
/* For the benefit of Windows, call gdb_select before reading from
the file. Wait until at least one byte of data is available.
Control-C can interrupt gdb_select, but not read. */
{
fd_set readfds;
FD_ZERO (&readfds);
FD_SET (stdio->fd, &readfds);
if (gdb_select (stdio->fd + 1, &readfds, NULL, NULL, NULL) == -1)
return -1;
}
return read (stdio->fd, buf, length_buf);
This is a race classically fixed with either the self-pipe trick, or
by blocking SIGINT and then using pselect instead of select.
Blocking SIGINT most of the time would mean that check_quit_flag (and
thus QUIT) would need to do a syscall every time it is called, which
sounds best avoided, since QUIT is called in many loops. Thus we take
the self-pipe trick route (wrapped in a serial event).
Instead of having all places that need this manually add an extra file
descriptor to the set of gdb_select's watched file descriptors, we
introduce a wrapper, interruptible_select, that does that.
The Windows version of gdb_select actually does not suffer from this,
because mingw-hdep.c:gdb_call_async_signal_handler sets a Windows
event that gdb_select always waits on. So this patch can be seen as
generalization of that technique. We can't remove that extra event
from mingw-hdep.c until we get rid of immediate_quit though.
gdb/ChangeLog:
2016-04-12 Pedro Alves <palves@redhat.com>
* defs.h: Extend QUIT-related comments to mention
interruptible_select.
(quit_serial_event_set, quit_serial_event_clear): Declare.
* event-top.c: Include "ser-event.h" and "gdb_select.h".
(quit_serial_event): New global.
(async_init_signals): Make quit_serial_event.
(quit_serial_event_set, quit_serial_event_clear)
(quit_serial_event_fd, interruptible_select): New functions.
* extension.c (set_quit_flag): Set the quit serial event.
(check_quit_flag): Clear the quit serial event.
* gdb_select.h (interruptible_select): New declaration.
* guile/scm-ports.c (ioscm_input_waiting): Use
interruptible_select instead of gdb_select.
* top.c (gdb_readline_no_editing): Likewise.
* ui-file.c (stdio_file_read): Likewise.
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| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| zlib | ||
| .cvsignore | ||
| .gitattributes | ||
| .gitignore | ||
| ChangeLog | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| COPYING.LIB | ||
| COPYING.LIBGLOSS | ||
| COPYING.NEWLIB | ||
| depcomp | ||
| djunpack.bat | ||
| install-sh | ||
| libtool.m4 | ||
| lt~obsolete.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| makefile.vms | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release.sh | ||
| symlink-tree | ||
| ylwrap | ||
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.