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authorPedro Alves <palves@redhat.com>2014-05-29 12:50:48 +0100
committerPedro Alves <palves@redhat.com>2014-05-29 12:50:48 +0100
commit8817a6f225766029787b5e2c1300a342b328909e (patch)
treeddd4b202fdfc37f17c2619576b1b71592c622daa /gdb/infrun.c
parent251bde03baf93dbb44d3785e09e03179916143e3 (diff)
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PR gdb/15713 - errors from i386_linux_resume lead to lock-up
linux_nat_resume is not considering that linux_ops->to_resume may throw: /* Mark LWP as not stopped to prevent it from being continued by linux_nat_resume_callback. */ lp->stopped = 0; if (resume_many) iterate_over_lwps (ptid, linux_nat_resume_callback, NULL); If something within linux_nat_resume_callback throws, GDB leaves the lwp_info as if the inferior was resumed, while it actually wasn't. A couple examples, there are possibly others: - i386_linux_resume calls target_read which calls QUIT. - if the actual ptrace resumption fails in inf_ptrace_resume, perror_with_name is called. If the user tries to kill the inferior at this point (or quit, which offers to kill), GDB locks up trying to stop the lwp -- if it is already stopped no new waitpid event gets generated for it. Fix this by setting the stopped flag earlier, as soon as we collect a stop event with waitpid, and clearing it always only after resuming the lwp successfully. Tested on x86_64 Fedora 20. Confirmed the lock-up disappears using a local hack that forces an error in inf_ptrace_resume. Also fixes a little "set debug lin-lwp" annoyance. Currently we always see: Continuing. LLR: Preparing to resume process 6802, 0, inferior_ptid Thread 0x7ffff7fc7740 (LWP 6802) ^^^^^^^^ RC: Resuming sibling Thread 0x7ffff77c5700 (LWP 6807), 0, resume RC: Resuming sibling Thread 0x7ffff7fc6700 (LWP 6806), 0, resume RC: Not resuming sibling Thread 0x7ffff7fc7740 (LWP 6802) (not stopped) ^^^^^^^^^^^^^^^^^^^^^^^ LLR: PTRACE_CONT process 6802, 0 (resume event thread) This patch gets rid of the "Not resuming sibling" line. 2014-05-29 Pedro Alves <palves@redhat.com> PR gdb/15713 * linux-nat.c (linux_nat_resume_callback): Rename the second parameter to 'except'. Skip LP if it points to EXCEPT. (linux_nat_resume): Don't mark the event lwp as not stopped before resuming sibling lwps. Instead ask linux_nat_resume_callback to skip the event lwp. Mark it as not stopped after actually resuming it. (linux_handle_syscall_trap): Mark the lwp as not stopped after resuming it. (wait_lwp): Mark the lwp as stopped here. (stop_wait_callback): Mark the lwp as not stopped right after resuming it. Don't mark lwps as stopped here. (linux_nat_filter_event): Mark the lwp as stopped earlier. (linux_nat_wait_1): Don't mark dead lwps as stopped here.
Diffstat (limited to 'gdb/infrun.c')
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