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infrun: scheduler-locking replay 

Record targets behave as if scheduler-locking were on in replay mode.  Add a
new scheduler-locking option "replay" to make this implicit behaviour explicit.
It behaves like "on" in replay mode and like "off" in record mode.

By making the current behaviour a scheduler-locking option, we allow the user
to change it.  Since it is the current behaviour, this new option is also
the new default.

One caveat is that when resuming a thread that is at the end of its execution
history, record btrace implicitly stops replaying other threads and resumes
the entire process.  This is a convenience feature to not require the user
to explicitly move all other threads to the end of their execution histories
before being able to resume the process.

We mimick this behaviour with scheduler-locking replay and move it from
record-btrace into infrun.  With all-stop on top of non-stop, we can't do
this in record-btrace anymore.

Record full does not really support multi-threading and is therefore not
impacted.  If it were extended to support multi-threading, it would 'benefit'
from this change.  The good thing is that all record targets will behave the
same with respect to scheduler-locking.

I put the code for this into clear_proceed_status.  It also sends the
about_to_proceed notification.

gdb/
	* NEWS: Announce new scheduler-locking mode.
	* infrun.c (schedlock_replay): New.
	(scheduler_enums): Add schedlock_replay.
	(scheduler_mode): Change default to schedlock_replay.
	(user_visible_resume_ptid): Handle schedlock_replay.
	(clear_proceed_status_thread): Stop replaying if resumed thread is
	not replaying.
	(schedlock_applies): Handle schedlock_replay.
	(_initialize_infrun): Document new scheduler-locking mode.
	* record-btrace.c (record_btrace_resume): Remove code to stop other
	threads when not replaying the resumed thread.

doc/
	* gdb.texinfo (All-Stop Mode): Describe new scheduler-locking mode.
This commit is contained in:
Markus Metzger 2015-09-07 15:41:00 +02:00
parent 7ff27e9bab
commit f2665db5f2
6 changed files with 70 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
gdb/ChangeLog
View File

@ -1,3 +1,17 @@
2015-09-18 Markus Metzger <markus.t.metzger@intel.com>
* NEWS: Announce new scheduler-locking mode.
* infrun.c (schedlock_replay): New.
(scheduler_enums): Add schedlock_replay.
(scheduler_mode): Change default to schedlock_replay.
(user_visible_resume_ptid): Handle schedlock_replay.
(clear_proceed_status_thread): Stop replaying if resumed thread is
not replaying.
(schedlock_applies): Handle schedlock_replay.
(_initialize_infrun): Document new scheduler-locking mode.
* record-btrace.c (record_btrace_resume): Remove code to stop other
threads when not replaying the resumed thread.
2015-09-18 Markus Metzger <markus.t.metzger@intel.com>
* record-btrace.c ((record_btrace_will_replay): New.

3
gdb/NEWS
View File

@ -45,6 +45,9 @@ show remote multiprocess-extensions-packet
The "/m" option is now considered deprecated: its "source-centric"
output hasn't proved useful in practice.
* The "set scheduler-locking" command supports a new mode "replay".
It behaves like "off" in record mode and like "on" in replay mode.
* Support for various ROM monitors has been removed:
target dbug dBUG ROM monitor for Motorola ColdFire

4
gdb/doc/ChangeLog
View File

@ -1,3 +1,7 @@
2015-09-18 Markus Metzger <markus.t.metzger@intel.com>
* gdb.texinfo (All-Stop Mode): Describe new scheduler-locking mode.
2015-09-15 Pedro Alves <palves@redhat.com>
PR remote/18965

25
gdb/doc/gdb.texinfo
View File

@ -5836,17 +5836,20 @@ locking the OS scheduler to allow only a single thread to run.
@item set scheduler-locking @var{mode}
@cindex scheduler locking mode
@cindex lock scheduler
Set the scheduler locking mode. If it is @code{off}, then there is no
locking and any thread may run at any time. If @code{on}, then only the
current thread may run when the inferior is resumed. The @code{step}
mode optimizes for single-stepping; it prevents other threads
from preempting the current thread while you are stepping, so that
the focus of debugging does not change unexpectedly.
Other threads never get a chance to run when you step, and they are
completely free to run when you use commands
like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
thread hits a breakpoint during its timeslice, @value{GDBN} does not change
the current thread away from the thread that you are debugging.
Set the scheduler locking mode. It applies to normal execution,
record mode, and replay mode. If it is @code{off}, then there is no
locking and any thread may run at any time. If @code{on}, then only
the current thread may run when the inferior is resumed. The
@code{step} mode optimizes for single-stepping; it prevents other
threads from preempting the current thread while you are stepping, so
that the focus of debugging does not change unexpectedly. Other
threads never get a chance to run when you step, and they are
completely free to run when you use commands like @samp{continue},
@samp{until}, or @samp{finish}. However, unless another thread hits a
breakpoint during its timeslice, @value{GDBN} does not change the
current thread away from the thread that you are debugging. The
@code{replay} mode behaves like @code{off} in record mode and like
@code{on} in replay mode.
@item show scheduler-locking
Display the current scheduler locking mode.

39
gdb/infrun.c
View File

@ -2166,13 +2166,15 @@ resume_cleanups (void *ignore)
static const char schedlock_off[] = "off";
static const char schedlock_on[] = "on";
static const char schedlock_step[] = "step";
static const char schedlock_replay[] = "replay";
static const char *const scheduler_enums[] = {
schedlock_off,
schedlock_on,
schedlock_step,
schedlock_replay,
NULL
};
static const char *scheduler_mode = schedlock_off;
static const char *scheduler_mode = schedlock_replay;
static void
show_scheduler_mode (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
@ -2238,6 +2240,13 @@ user_visible_resume_ptid (int step)
resume. */
resume_ptid = inferior_ptid;
}
else if ((scheduler_mode == schedlock_replay)
&& target_record_will_replay (minus_one_ptid, execution_direction))
{
/* User-settable 'scheduler' mode requires solo thread resume in replay
mode. */
resume_ptid = inferior_ptid;
}
else if (!sched_multi && target_supports_multi_process ())
{
/* Resume all threads of the current process (and none of other
@ -2803,6 +2812,18 @@ clear_proceed_status_thread (struct thread_info *tp)
void
clear_proceed_status (int step)
{
/* With scheduler-locking replay, stop replaying other threads if we're
not replaying the user-visible resume ptid.
This is a convenience feature to not require the user to explicitly
stop replaying the other threads. We're assuming that the user's
intent is to resume tracing the recorded process. */
if (!non_stop && scheduler_mode == schedlock_replay
&& target_record_is_replaying (minus_one_ptid)
&& !target_record_will_replay (user_visible_resume_ptid (step),
execution_direction))
target_record_stop_replaying ();
if (!non_stop)
{
struct thread_info *tp;
@ -2890,7 +2911,10 @@ schedlock_applies (struct thread_info *tp)
{
return (scheduler_mode == schedlock_on
|| (scheduler_mode == schedlock_step
&& tp->control.stepping_command));
&& tp->control.stepping_command)
|| (scheduler_mode == schedlock_replay
&& target_record_will_replay (minus_one_ptid,
execution_direction)));
}
/* Basic routine for continuing the program in various fashions.
@ -9187,10 +9211,13 @@ By default, the debugger will use the same inferior."),
scheduler_enums, &scheduler_mode, _("\
Set mode for locking scheduler during execution."), _("\
Show mode for locking scheduler during execution."), _("\
off == no locking (threads may preempt at any time)\n\
on == full locking (no thread except the current thread may run)\n\
step == scheduler locked during stepping commands (step, next, stepi, nexti).\n\
In this mode, other threads may run during other commands."),
off == no locking (threads may preempt at any time)\n\
on == full locking (no thread except the current thread may run)\n\
This applies to both normal execution and replay mode.\n\
step == scheduler locked during stepping commands (step, next, stepi, nexti).\n\
In this mode, other threads may run during other commands.\n\
This applies to both normal execution and replay mode.\n\
replay == scheduler locked in replay mode and unlocked during normal execution."),
set_schedlock_func, /* traps on target vector */
show_scheduler_mode,
&setlist, &showlist);

10
gdb/record-btrace.c
View File

@ -1903,22 +1903,16 @@ record_btrace_resume (struct target_ops *ops, ptid_t ptid, int step,
to not change the execution direction in-between. */
record_btrace_resume_exec_dir = execution_direction;
/* For all-stop targets... */
/* For all-stop targets we pick the current thread when asked to resume an
entire process or everything. */
if (!target_is_non_stop_p ())
{
/* ...we pick the current thread when asked to resume an entire process
or everything. */
if (ptid_equal (minus_one_ptid, ptid) || ptid_is_pid (ptid))
ptid = inferior_ptid;
tp = find_thread_ptid (ptid);
if (tp == NULL)
error (_("Cannot find thread to resume."));
/* ...and we stop replaying other threads if the thread to resume is not
replaying. */
if (!btrace_is_replaying (tp) && execution_direction != EXEC_REVERSE)
target_record_stop_replaying ();
}
/* As long as we're not replaying, just forward the request.