Re: [RFA/doco] Document task-specific breakpoints

Joel Brobecker
2009-03-26T22:39:19Z

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Hello Eli,

> > +Breakpoint 5, test_task_debug.tB.1 (_task=0x11ffffc60)
> ^^^^^
> What is this part? Should we explain it in some footnote? And what
> about _task=0x11ffffc60 part, should it perhaps be explained, too?

Hmm, good point. These are actually old compiler artifacts that we
got rid of since writing that documentation. The original testcase
was using what we call a task "entry" I believe, which is the reason
for the "_task" parameter. We could just as well have used a function
so I cleaned up the example to make it simpler.

> > +(@value{GDBP}) info tasks
> > + ID TID P-ID Pri State Name
> > + 1 140022020 0 15 Child Activation Wait main_task
> > +* 2 140045060 1 15 Running t2
>
> "Running"? shouldn't it be stopped at breakpoint?

In practice, yes, it is stopped. But this information is printed
from the point of view of the runtime. To the runtime, task "t2"
is running.

Attached is a new version of the documentation patch:

* gdb.texinfo (Ada Tasks): Add documentation about task-specific
breakpoints.
(Set Breaks): Add reference to thread-specific and task-specific
breakpoints.

Thanks,
--
Joel

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diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 134919d..77b522b 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -3051,6 +3051,11 @@ C@t{++}, a function name may refer to more than one possible place to break.
@xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
that situation.

+It is also possible to insert a breakpoint that will stop the program
+only if a specific thread or a specific task hits that breakpoint.
+@xref{Thread-Specific Breakpoints} and @ref{Ada Tasks} for more
+information about this feature.
+
@item break
When called without any arguments, @code{break} sets a breakpoint at
the next instruction to be executed in the selected stack frame
@@ -11743,6 +11748,58 @@ from the current task to the given task.
#4 0x804aacc in un () at un.adb:5
@end smallexample

+@item break @var{linespec} task @var{taskno}
+@itemx break @var{linespec} task @var{taskno} if @dots{}
+@cindex breakpoints and tasks, in Ada
+@cindex task breakpoints, in Ada
+@kindex break @dots{} task @var{taskno}@r{ (Ada)}
+These commands are like the @code{break @dots{} thread @dots{}}
+command (@pxref{Thread Stops}).
+@var{linespec} specifies source lines, as described
+in @ref{Specify Location}.
+
+Use the qualifier @samp{task @var{taskno}} with a breakpoint command
+to specify that you only want @value{GDBN} to stop the program when a
+particular Ada task reaches this breakpoint. @var{taskno} is one of the
+numeric task identifiers assigned by @value{GDBN}, shown in the first
+column of the @samp{info tasks} display.
+
+If you do not specify @samp{task @var{taskno}} when you set a
+breakpoint, the breakpoint applies to @emph{all} tasks of your
+program.
+
+You can use the @code{task} qualifier on conditional breakpoints as
+well; in this case, place @samp{task @var{taskno}} before the
+breakpoint condition (before the @code{if}).
+
+For example,
+
+@smallexample
+@iftex
+@leftskip=0.5cm
+@end iftex
+(@value{GDBP}) info tasks
+ ID TID P-ID Pri State Name
+ 1 140022020 0 15 Child Activation Wait main_task
+ 2 140045060 1 15 Accept/Select Wait t2
+ 3 140044840 1 15 Runnable t1
+* 4 140056040 1 15 Running t3
+(@value{GDBP}) b 15 task 2
+Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
+(@value{GDBP}) cont
+Continuing.
+task # 1 running
+task # 2 running
+
+Breakpoint 5, test_task_debug () at test_task_debug.adb:15
+15 flush;
+(@value{GDBP}) info tasks
+ ID TID P-ID Pri State Name
+ 1 140022020 0 15 Child Activation Wait main_task
+* 2 140045060 1 15 Running t2
+ 3 140044840 1 15 Runnable t1
+ 4 140056040 1 15 Delay Sleep t3
+@end smallexample
@end table

@node Ada Tasks and Core Files