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gdb/linux-nat: remove check based on current_inferior in linux_handle_extended_wait

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The check removed by this patch, using current_inferior, looks wrong.
When debugging multiple inferiors with the Linux native target and
linux_handle_extended_wait is called, there's no guarantee about which
is the current inferior.  The vfork-done event we receive could be for
any inferior.  If the vfork-done event is for a non-current inferior, we
end up wrongfully ignoring it.  As a result, the core never processes a
TARGET_WAITKIND_VFORK_DONE event, program_space::breakpoints_not_allowed
is never cleared, and breakpoints are never reinserted.  However,
because the Linux native target decided to ignore the event, it resumed
the thread - while breakpoints out.  And that's bad.

The proposed fix is to remove this check.  Always report vfork-done
events and let infrun's logic decide if it should be ignored.  We don't
save much cycles by filtering the event here.

Add a test that replicates the situation described above.  See comments
in the test for more details.

Change-Id: Ibe33c1716c3602e847be6c2093120696f2286fbf
This commit is contained in:
Simon Marchi
2022-01-17 11:27:36 -05:00
parent 20471e00e2
commit 5a0c4a06eb
4 changed files with 199 additions and 13 deletions
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17
gdb/linux-nat.c
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@@ -1990,20 +1990,11 @@ linux_handle_extended_wait (struct lwp_info *lp, int status)
if (event == PTRACE_EVENT_VFORK_DONE)
{
if (current_inferior ()->waiting_for_vfork_done)
{
linux_nat_debug_printf
("Got expected PTRACE_EVENT_VFORK_DONE from LWP %ld: stopping",
lp->ptid.lwp ());
ourstatus->set_vfork_done ();
return 0;
}
linux_nat_debug_printf
("Got PTRACE_EVENT_VFORK_DONE from LWP %ld: ignoring", lp->ptid.lwp ());
return 1;
("Got PTRACE_EVENT_VFORK_DONE from LWP %ld",
lp->ptid.lwp ());
ourstatus->set_vfork_done ();
return 0;
}
internal_error (__FILE__, __LINE__,