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Say: <stopped at a breakpoint in thread 2> (gdb) thread 3 (gdb) step The above triggers the prepare_to_proceed/deferred_step_ptid process, which switches back to thread 2, to step over its breakpoint before getting back to thread 3 and "step" it. If while stepping over the breakpoint in thread 2, a signal arrives, and it is set to pass/nostop, we'll set a step-resume breakpoint at the supposed signal-handler resume address, and call keep_going. The problem is that we were supposedly stepping thread 3, and that keep_going delivers a signal to thread 2, and due to scheduler-locking off, resumes everything else, _including_ thread 3, the thread we want stepping. This means that we lose control of thread 3 until the next event, when we stop everything. The end result for the user, is that GDB lost control of the "step". Here's the current infrun debug output of the above, with the testcase in the patch below: infrun: clear_proceed_status_thread (Thread 0x2aaaab8f5700 (LWP 11663)) infrun: clear_proceed_status_thread (Thread 0x2aaaab6f4700 (LWP 11662)) infrun: clear_proceed_status_thread (Thread 0x2aaaab4f2b20 (LWP 11659)) infrun: proceed (addr=0xffffffffffffffff, signal=144, step=1) infrun: prepare_to_proceed (step=1), switched to [Thread 0x2aaaab6f4700 (LWP 11662)] infrun: resume (step=1, signal=0), trap_expected=1, current thread [Thread 0x2aaaab6f4700 (LWP 11662)] at 0x40098f infrun: wait_for_inferior () infrun: target_wait (-1, status) = infrun: 11659 [Thread 0x2aaaab6f4700 (LWP 11662)], infrun: status->kind = stopped, signal = SIGUSR1 infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x40098f infrun: random signal 30 Program received signal SIGUSR1, User defined signal 1. infrun: signal arrived while stepping over breakpoint infrun: inserting step-resume breakpoint at 0x40098f infrun: resume (step=0, signal=30), trap_expected=0, current thread [Thread 0x2aaaab6f4700 (LWP 11662)] at 0x40098f ^^^ this is a wildcard resume. infrun: prepare_to_wait infrun: target_wait (-1, status) = infrun: 11659 [Thread 0x2aaaab6f4700 (LWP 11662)], infrun: status->kind = stopped, signal = SIGTRAP infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x40098f infrun: BPSTAT_WHAT_STEP_RESUME infrun: resume (step=1, signal=0), trap_expected=1, current thread [Thread 0x2aaaab6f4700 (LWP 11662)] at 0x40098f ^^^ step-resume hit, meaning the handler returned, so we go back to stepping thread 3. infrun: prepare_to_wait infrun: target_wait (-1, status) = infrun: 11659 [Thread 0x2aaaab6f4700 (LWP 11662)], infrun: status->kind = stopped, signal = SIGTRAP infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x40088b infrun: switching back to stepped thread infrun: Switching context from Thread 0x2aaaab6f4700 (LWP 11662) to Thread 0x2aaaab8f5700 (LWP 11663) infrun: resume (step=1, signal=0), trap_expected=0, current thread [Thread 0x2aaaab8f5700 (LWP 11663)] at 0x400938 infrun: prepare_to_wait infrun: target_wait (-1, status) = infrun: 11659 [Thread 0x2aaaab8f5700 (LWP 11663)], infrun: status->kind = stopped, signal = SIGTRAP infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x40093a infrun: keep going infrun: resume (step=1, signal=0), trap_expected=0, current thread [Thread 0x2aaaab8f5700 (LWP 11663)] at 0x40093a infrun: prepare_to_wait infrun: target_wait (-1, status) = infrun: 11659 [Thread 0x2aaaab8f5700 (LWP 11663)], infrun: status->kind = stopped, signal = SIGTRAP infrun: infwait_normal_state infrun: TARGET_WAITKIND_STOPPED infrun: stop_pc = 0x40091e infrun: stepped to a different line infrun: stop_stepping [Switching to Thread 0x2aaaab8f5700 (LWP 11663)] 69 (*myp) ++; /* set breakpoint child_two here */ ^^^ we stopped at the wrong line. We still stepped a bit because the test is running in a loop, and when we got back to stepping thread 3, it happened to be in the stepping range. (The loop increments a counter, and the test makes sure it increments exactly once. Without the fix, the counter increments a bunch, since the user-stepped thread runs free without GDB noticing.) The fix is to switch to the stepping thread before continuing for the step-resume breakpoint. gdb/ 2014-02-07 Pedro Alves <palves@redhat.com> * infrun.c (handle_signal_stop) <signal arrives while stepping over a breakpoint>: Switch back to the stepping thread. gdb/testsuite/ 2014-02-07 Pedro Alves <pedro@codesourcery.com> Pedro Alves <palves@redhat.com> * gdb.threads/step-after-sr-lock.c: New file. * gdb.threads/step-after-sr-lock.exp: New file. |
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bfd | ||
binutils | ||
config | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
.cvsignore | ||
.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 | ||
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.