4dd63d488a
When a program forks and another process start threads while gdb is
handling the fork event, newly created threads are left stuck stopped
by gdb, even though gdb presents them as "running", to the user.
This can be seen with the test added by this patch. The test has the
inferior fork a certain number of times and waits for all children to
exit. Each fork child spawns a number of threads that do nothing and
joins them immediately. Normally, the program should run unimpeded
(from the point of view of the user) and exit very quickly. Without
this fix, it doesn't because of some threads left stopped by gdb, so
inferior 1 never exits.
The program triggers when a new clone thread is found while inside the
linux_stop_and_wait_all_lwps call in linux-thread-db.c:
linux_stop_and_wait_all_lwps ();
ALL_LWPS (lp)
if (ptid_get_pid (lp->ptid) == pid)
thread_from_lwp (lp->ptid);
linux_unstop_all_lwps ();
Within linux_stop_and_wait_all_lwps, we reach
linux_handle_extended_wait with the "stopping" parameter set to 1, and
because of that we don't mark the new lwp as resumed. As consequence,
the subsequent resume_stopped_resumed_lwps, called from
linux_unstop_all_lwps, never resumes the new LWP.
There's lots of cruft in linux_handle_extended_wait that no longer
makes sense. On systems with CLONE events support, we don't rely on
libthread_db for thread listing anymore, so the code that preserves
stop_requested and the handling of last_resume_kind is all dead.
So the fix is to remove all that, and simply always mark the new LWP
as resumed, so that resume_stopped_resumed_lwps re-resumes it.
gdb/ChangeLog:
2015-07-30 Pedro Alves <palves@redhat.com>
Simon Marchi <simon.marchi@ericsson.com>
PR threads/18600
* linux-nat.c (linux_handle_extended_wait): On CLONE event, always
mark the new thread as resumed. Remove STOPPING parameter.
(wait_lwp): Adjust call to linux_handle_extended_wait.
(linux_nat_filter_event): Adjust call to
linux_handle_extended_wait.
(resume_stopped_resumed_lwps): Add debug output.
gdb/testsuite/ChangeLog:
2015-07-30 Simon Marchi <simon.marchi@ericsson.com>
Pedro Alves <palves@redhat.com>
PR threads/18600
* gdb.threads/fork-plus-threads.c: New file.
* gdb.threads/fork-plus-threads.exp: New file.
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| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
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| opcodes | ||
| readline | ||
| sim | ||
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| zlib | ||
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| ChangeLog | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
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| depcomp | ||
| djunpack.bat | ||
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| ltsugar.m4 | ||
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| MAINTAINERS | ||
| Makefile.def | ||
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| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| README | ||
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| setup.com | ||
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| 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.