b57bacecd5
Commit a25a5a45 (Fix "breakpoint always-inserted off"; remove
"breakpoint always-inserted auto") regressed non-stop remote
debugging.
This was exposed by mi-nsintrall.exp intermittently failing with a
spurious SIGTRAP.
The problem is that when debugging with "target remote", new threads
the target has spawned but have never reported a stop aren't visible
to GDB until it explicitly resyncs its thread list with the target's.
For example, in a program like this:
int
main (void)
{
pthread_t child_thread;
pthread_create (&child_thread, NULL, child_function, NULL);
return 0; <<<< set breakpoint here
}
If the user sets a breakpoint at the "return" statement, and runs the
program, when that breakpoint hit is reported, GDB is only aware of
the main thread. So if we base the decision to remove or insert
breakpoints from the target based on whether all the threads we know
about are stopped, we'll miss that child_thread is running, and thus
we'll remove breakpoints from the target, even through they should
still remain inserted, otherwise child_thread will miss them.
The break-while-running.exp test actually should also be exposing this
thread-list-out-of-synch problem. That test sets a breakpoint while
the main thread is stopped, but other threads are running. Because
other threads are running, the breakpoint is supposed to be inserted
immediately. But, unless something forces a refetch of the thread
list, like, e.g., "info threads", GDB won't be aware of the other
threads that had been spawned by the main thread, and so won't insert
new or old breakpoints in the target. And it turns out that the test
is exactly doing an explicit "info threads", masking out the
problem... This commit adjust the test to exercise the case of not
issuing "info threads". The test then fails without the GDB fix.
In the ni-nsintrall.exp case, what happens is that several threads hit
the same breakpoint, and when the first thread reports the stop,
because GDB wasn't aware other threads exist, all threads known to GDB
are found stopped, so GDB removes the breakpoints from the target.
The other threads follow up with SIGTRAPs too for that same
breakpoint, which has already been removed. For the first few
threads, the moribund breakpoints machinery suppresses the SIGTRAPs,
but after a few events (precisely '3 * thread_count () + 1' at the
time the breakpoint was removed, see update_global_location_list), the
moribund breakpoint machinery is no longer aware of the removed
breakpoint, and the SIGTRAP is reported as a spurious stop.
The fix is naturally then to stop assuming that if no thread in the
list is executing, then the target is fully stopped. We can't know
that until we fully sync the thread list. Because updating the thread
list on every stop would be too much RSP traffic, I chose instead to
update it whenever we're about to present a stop to the user.
Actually updating the thread list at that point happens to be an item
I had added to the local/remote parity wiki page a while ago:
Native GNU/Linux debugging adds new threads to the thread list as
the program creates them "The [New Thread foo] messages". Remote
debugging can't do that, and it's arguable whether we shouldn't even
stop native debugging from doing that, as it hinders inferior
performance. However, a related issue is that with remote targets
(and gdbserver), even after the program stops, the user still needs
to do "info threads" to pull an updated thread list. This, should
most likely be addressed, so that GDB pulls the list itself, perhaps
just before presenting a stop to the user.
With that in place, the need to delay "Program received signal FOO"
was actually caught by the manythreads.exp test. Without that bit, I
was getting:
[Thread 0x7ffff7f13700 (LWP 4499) exited]
[New Thread 0x7ffff7f0b700 (LWP 4500)]
^C
Program received signal SIGINT, Interrupt.
[New Thread 0x7ffff7f03700 (LWP 4501)] <<< new output
[Switching to Thread 0x7ffff7f0b700 (LWP 4500)]
__GI___nptl_death_event () at events.c:31
31 {
(gdb) FAIL: gdb.threads/manythreads.exp: stop threads 1
That is, I was now getting "New Thread" lines after the "Program
received signal" line, and the test doesn't expect them. As the
number of new threads discovered before and after the "Program
received signal" output is unbounded, it's much nicer to defer
"Program received signal" until after synching the thread list, thus
close to the "switching to thread" output and "current frame/source"
info:
[Thread 0x7ffff7863700 (LWP 7647) exited]
^C[New Thread 0x7ffff786b700 (LWP 7648)]
Program received signal SIGINT, Interrupt.
[Switching to Thread 0x7ffff7fc4740 (LWP 6243)]
__GI___nptl_create_event () at events.c:25
25 {
(gdb) PASS: gdb.threads/manythreads.exp: stop threads 1
Tested on x86_64 Fedora 20, native and gdbserver.
gdb/
2014-10-02 Pedro Alves <palves@redhat.com>
* breakpoint.c (breakpoints_should_be_inserted_now): Use
threads_are_executing.
* breakpoint.h (breakpoints_should_be_inserted_now): Add
describing comment.
* gdbthread.h (threads_are_executing): Declare.
(handle_signal_stop) <random signals>: Don't print about the
signal here if stopping.
(end_stepping_range): Don't notify observers here.
(normal_stop): Update the thread list. If stopped by a random
signal or a stepping range ended, notify observers.
* thread.c (threads_executing): New global.
(init_thread_list): Clear 'threads_executing'.
(set_executing): Set or clear 'threads_executing'.
(threads_are_executing): New function.
(update_threads_executing): New function.
(update_thread_list): Use it.
gdb/testsuite/
2014-10-02 Pedro Alves <palves@redhat.com>
* gdb.threads/break-while-running.exp (test): Add new
'update_thread_list' argument. Skip "info threads" if false.
(top level): Add new 'update_thread_list' axis.
428 lines
16 KiB
C
428 lines
16 KiB
C
/* Multi-process/thread control defs for GDB, the GNU debugger.
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Copyright (C) 1987-2014 Free Software Foundation, Inc.
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Contributed by Lynx Real-Time Systems, Inc. Los Gatos, CA.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef GDBTHREAD_H
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#define GDBTHREAD_H
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struct symtab;
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#include "breakpoint.h"
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#include "frame.h"
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#include "ui-out.h"
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#include "inferior.h"
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#include "btrace.h"
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/* Frontend view of the thread state. Possible extensions: stepping,
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finishing, until(ling),... */
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enum thread_state
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{
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THREAD_STOPPED,
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THREAD_RUNNING,
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THREAD_EXITED,
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};
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/* Inferior thread specific part of `struct infcall_control_state'.
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Inferior process counterpart is `struct inferior_control_state'. */
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struct thread_control_state
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{
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/* User/external stepping state. */
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/* Step-resume or longjmp-resume breakpoint. */
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struct breakpoint *step_resume_breakpoint;
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/* Exception-resume breakpoint. */
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struct breakpoint *exception_resume_breakpoint;
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/* Range to single step within.
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If this is nonzero, respond to a single-step signal by continuing
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to step if the pc is in this range.
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If step_range_start and step_range_end are both 1, it means to
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step for a single instruction (FIXME: it might clean up
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wait_for_inferior in a minor way if this were changed to the
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address of the instruction and that address plus one. But maybe
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not). */
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CORE_ADDR step_range_start; /* Inclusive */
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CORE_ADDR step_range_end; /* Exclusive */
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/* If GDB issues a target step request, and this is nonzero, the
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target should single-step this thread once, and then continue
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single-stepping it without GDB core involvement as long as the
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thread stops in the step range above. If this is zero, the
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target should ignore the step range, and only issue one single
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step. */
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int may_range_step;
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/* Stack frame address as of when stepping command was issued.
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This is how we know when we step into a subroutine call, and how
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to set the frame for the breakpoint used to step out. */
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struct frame_id step_frame_id;
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/* Similarly, the frame ID of the underlying stack frame (skipping
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any inlined frames). */
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struct frame_id step_stack_frame_id;
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/* Nonzero if we are presently stepping over a breakpoint.
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If we hit a breakpoint or watchpoint, and then continue, we need
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to single step the current thread with breakpoints disabled, to
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avoid hitting the same breakpoint or watchpoint again. And we
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should step just a single thread and keep other threads stopped,
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so that other threads don't miss breakpoints while they are
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removed.
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So, this variable simultaneously means that we need to single
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step the current thread, keep other threads stopped, and that
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breakpoints should be removed while we step.
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This variable is set either:
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- in proceed, when we resume inferior on user's explicit request
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- in keep_going, if handle_inferior_event decides we need to
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step over breakpoint.
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The variable is cleared in normal_stop. The proceed calls
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wait_for_inferior, which calls handle_inferior_event in a loop,
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and until wait_for_inferior exits, this variable is changed only
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by keep_going. */
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int trap_expected;
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/* Nonzero if the thread is being proceeded for a "finish" command
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or a similar situation when stop_registers should be saved. */
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int proceed_to_finish;
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/* Nonzero if the thread is being proceeded for an inferior function
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call. */
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int in_infcall;
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enum step_over_calls_kind step_over_calls;
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/* Nonzero if stopped due to a step command. */
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int stop_step;
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/* Chain containing status of breakpoint(s) the thread stopped
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at. */
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bpstat stop_bpstat;
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/* The interpreter that issued the execution command. NULL if the
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thread was resumed as a result of a command applied to some other
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thread (e.g., "next" with scheduler-locking off). */
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struct interp *command_interp;
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};
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/* Inferior thread specific part of `struct infcall_suspend_state'.
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Inferior process counterpart is `struct inferior_suspend_state'. */
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struct thread_suspend_state
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{
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/* Last signal that the inferior received (why it stopped). When
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the thread is resumed, this signal is delivered. Note: the
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target should not check whether the signal is in pass state,
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because the signal may have been explicitly passed with the
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"signal" command, which overrides "handle nopass". If the signal
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should be suppressed, the core will take care of clearing this
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before the target is resumed. */
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enum gdb_signal stop_signal;
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};
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struct thread_info
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{
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struct thread_info *next;
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ptid_t ptid; /* "Actual process id";
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In fact, this may be overloaded with
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kernel thread id, etc. */
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int num; /* Convenient handle (GDB thread id) */
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/* The name of the thread, as specified by the user. This is NULL
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if the thread does not have a user-given name. */
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char *name;
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/* Non-zero means the thread is executing. Note: this is different
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from saying that there is an active target and we are stopped at
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a breakpoint, for instance. This is a real indicator whether the
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thread is off and running. */
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int executing;
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/* Frontend view of the thread state. Note that the THREAD_RUNNING/
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THREAD_STOPPED states are different from EXECUTING. When the
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thread is stopped internally while handling an internal event,
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like a software single-step breakpoint, EXECUTING will be false,
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but STATE will still be THREAD_RUNNING. */
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enum thread_state state;
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/* If this is > 0, then it means there's code out there that relies
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on this thread being listed. Don't delete it from the lists even
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if we detect it exiting. */
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int refcount;
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/* State of GDB control of inferior thread execution.
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See `struct thread_control_state'. */
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struct thread_control_state control;
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/* State of inferior thread to restore after GDB is done with an inferior
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call. See `struct thread_suspend_state'. */
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struct thread_suspend_state suspend;
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int current_line;
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struct symtab *current_symtab;
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/* Internal stepping state. */
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/* Record the pc of the thread the last time it stopped. This is
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maintained by proceed and keep_going, and used in
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adjust_pc_after_break to distinguish a hardware single-step
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SIGTRAP from a breakpoint SIGTRAP. */
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CORE_ADDR prev_pc;
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/* Should we step over breakpoint next time keep_going is called? */
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int stepping_over_breakpoint;
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/* Set to TRUE if we should finish single-stepping over a breakpoint
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after hitting the current step-resume breakpoint. The context here
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is that GDB is to do `next' or `step' while signal arrives.
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When stepping over a breakpoint and signal arrives, GDB will attempt
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to skip signal handler, so it inserts a step_resume_breakpoint at the
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signal return address, and resume inferior.
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step_after_step_resume_breakpoint is set to TRUE at this moment in
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order to keep GDB in mind that there is still a breakpoint to step over
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when GDB gets back SIGTRAP from step_resume_breakpoint. */
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int step_after_step_resume_breakpoint;
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/* Per-thread command support. */
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/* Pointer to what is left to do for an execution command after the
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target stops. Used only in asynchronous mode, by targets that
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support async execution. Several execution commands use it. */
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struct continuation *continuations;
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/* Similar to the above, but used when a single execution command
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requires several resume/stop iterations. Used by the step
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command. */
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struct continuation *intermediate_continuations;
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/* If stepping, nonzero means step count is > 1 so don't print frame
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next time inferior stops if it stops due to stepping. */
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int step_multi;
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/* This is used to remember when a fork or vfork event was caught by
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a catchpoint, and thus the event is to be followed at the next
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resume of the thread, and not immediately. */
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struct target_waitstatus pending_follow;
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/* True if this thread has been explicitly requested to stop. */
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int stop_requested;
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/* The initiating frame of a nexting operation, used for deciding
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which exceptions to intercept. If it is null_frame_id no
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bp_longjmp or bp_exception but longjmp has been caught just for
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bp_longjmp_call_dummy. */
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struct frame_id initiating_frame;
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/* Private data used by the target vector implementation. */
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struct private_thread_info *private;
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/* Function that is called to free PRIVATE. If this is NULL, then
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xfree will be called on PRIVATE. */
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void (*private_dtor) (struct private_thread_info *);
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/* Branch trace information for this thread. */
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struct btrace_thread_info btrace;
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};
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/* Create an empty thread list, or empty the existing one. */
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extern void init_thread_list (void);
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/* Add a thread to the thread list, print a message
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that a new thread is found, and return the pointer to
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the new thread. Caller my use this pointer to
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initialize the private thread data. */
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extern struct thread_info *add_thread (ptid_t ptid);
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/* Same as add_thread, but does not print a message
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about new thread. */
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extern struct thread_info *add_thread_silent (ptid_t ptid);
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/* Same as add_thread, and sets the private info. */
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extern struct thread_info *add_thread_with_info (ptid_t ptid,
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struct private_thread_info *);
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/* Delete an existing thread list entry. */
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extern void delete_thread (ptid_t);
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/* Delete an existing thread list entry, and be quiet about it. Used
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after the process this thread having belonged to having already
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exited, for example. */
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extern void delete_thread_silent (ptid_t);
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/* Delete a step_resume_breakpoint from the thread database. */
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extern void delete_step_resume_breakpoint (struct thread_info *);
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/* Delete an exception_resume_breakpoint from the thread database. */
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extern void delete_exception_resume_breakpoint (struct thread_info *);
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/* Translate the integer thread id (GDB's homegrown id, not the system's)
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into a "pid" (which may be overloaded with extra thread information). */
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extern ptid_t thread_id_to_pid (int);
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/* Translate a 'pid' (which may be overloaded with extra thread information)
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into the integer thread id (GDB's homegrown id, not the system's). */
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extern int pid_to_thread_id (ptid_t ptid);
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/* Boolean test for an already-known pid (which may be overloaded with
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extra thread information). */
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extern int in_thread_list (ptid_t ptid);
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/* Boolean test for an already-known thread id (GDB's homegrown id,
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not the system's). */
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extern int valid_thread_id (int thread);
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/* Search function to lookup a thread by 'pid'. */
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extern struct thread_info *find_thread_ptid (ptid_t ptid);
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/* Find thread by GDB user-visible thread number. */
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struct thread_info *find_thread_id (int num);
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/* Finds the first thread of the inferior given by PID. If PID is -1,
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returns the first thread in the list. */
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struct thread_info *first_thread_of_process (int pid);
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/* Returns any thread of process PID, giving preference to the current
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thread. */
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extern struct thread_info *any_thread_of_process (int pid);
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/* Returns any non-exited thread of process PID, giving preference to
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the current thread, and to not executing threads. */
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extern struct thread_info *any_live_thread_of_process (int pid);
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/* Change the ptid of thread OLD_PTID to NEW_PTID. */
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void thread_change_ptid (ptid_t old_ptid, ptid_t new_ptid);
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/* Iterator function to call a user-provided callback function
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once for each known thread. */
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typedef int (*thread_callback_func) (struct thread_info *, void *);
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extern struct thread_info *iterate_over_threads (thread_callback_func, void *);
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/* Traverse all threads, except those that have THREAD_EXITED
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state. */
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#define ALL_NON_EXITED_THREADS(T) \
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for (T = thread_list; T; T = T->next) \
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if ((T)->state != THREAD_EXITED)
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extern int thread_count (void);
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/* Switch from one thread to another. */
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extern void switch_to_thread (ptid_t ptid);
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/* Marks thread PTID is running, or stopped.
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If ptid_get_pid (PTID) is -1, marks all threads. */
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extern void set_running (ptid_t ptid, int running);
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/* Marks or clears thread(s) PTID as having been requested to stop.
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If PTID is MINUS_ONE_PTID, applies to all threads. If
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ptid_is_pid(PTID) is true, applies to all threads of the process
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pointed at by PTID. If STOP, then the THREAD_STOP_REQUESTED
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observer is called with PTID as argument. */
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extern void set_stop_requested (ptid_t ptid, int stop);
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/* NOTE: Since the thread state is not a boolean, most times, you do
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not want to check it with negation. If you really want to check if
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the thread is stopped,
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use (good):
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if (is_stopped (ptid))
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instead of (bad):
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if (!is_running (ptid))
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The latter also returns true on exited threads, most likelly not
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what you want. */
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/* Reports if in the frontend's perpective, thread PTID is running. */
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extern int is_running (ptid_t ptid);
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/* Is this thread listed, but known to have exited? We keep it listed
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(but not visible) until it's safe to delete. */
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extern int is_exited (ptid_t ptid);
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/* In the frontend's perpective, is this thread stopped? */
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extern int is_stopped (ptid_t ptid);
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/* Marks thread PTID as executing, or not. If ptid_get_pid (PTID) is -1,
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marks all threads.
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Note that this is different from the running state. See the
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description of state and executing fields of struct
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thread_info. */
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extern void set_executing (ptid_t ptid, int executing);
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/* Reports if thread PTID is executing. */
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extern int is_executing (ptid_t ptid);
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/* True if any (known or unknown) thread is or may be executing. */
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extern int threads_are_executing (void);
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/* Merge the executing property of thread PTID over to its thread
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state property (frontend running/stopped view).
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"not executing" -> "stopped"
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"executing" -> "running"
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"exited" -> "exited"
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If ptid_get_pid (PTID) is -1, go over all threads.
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Notifications are only emitted if the thread state did change. */
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extern void finish_thread_state (ptid_t ptid);
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/* Same as FINISH_THREAD_STATE, but with an interface suitable to be
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registered as a cleanup. PTID_P points to the ptid_t that is
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passed to FINISH_THREAD_STATE. */
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extern void finish_thread_state_cleanup (void *ptid_p);
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/* Commands with a prefix of `thread'. */
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extern struct cmd_list_element *thread_cmd_list;
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/* Print notices on thread events (attach, detach, etc.), set with
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`set print thread-events'. */
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extern int print_thread_events;
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extern void print_thread_info (struct ui_out *uiout, char *threads,
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int pid);
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extern struct cleanup *make_cleanup_restore_current_thread (void);
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/* Returns a pointer into the thread_info corresponding to
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INFERIOR_PTID. INFERIOR_PTID *must* be in the thread list. */
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extern struct thread_info* inferior_thread (void);
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extern void update_thread_list (void);
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/* Return true if PC is in the stepping range of THREAD. */
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int pc_in_thread_step_range (CORE_ADDR pc, struct thread_info *thread);
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extern struct thread_info *thread_list;
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#endif /* GDBTHREAD_H */
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