visus
/
toolchain-gcc-arm-embedded

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2020 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
and with the Back-Cover Texts as in (a) below.

(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual.  Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom." -->
<!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Remote Non-Stop (Debugging with GDB)</title>

<meta name="description" content="Remote Non-Stop (Debugging with GDB)">
<meta name="keywords" content="Remote Non-Stop (Debugging with GDB)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<link href="index.html#Top" rel="start" title="Top">
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Remote-Protocol.html#Remote-Protocol" rel="up" title="Remote Protocol">
<link href="Packet-Acknowledgment.html#Packet-Acknowledgment" rel="next" title="Packet Acknowledgment">
<link href="Notification-Packets.html#Notification-Packets" rel="prev" title="Notification Packets">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smalllisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<a name="Remote-Non_002dStop"></a>
<div class="header">
<p>
Next: <a href="Packet-Acknowledgment.html#Packet-Acknowledgment" accesskey="n" rel="next">Packet Acknowledgment</a>, Previous: <a href="Notification-Packets.html#Notification-Packets" accesskey="p" rel="prev">Notification Packets</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Remote-Protocol-Support-for-Non_002dStop-Mode"></a>
<h3 class="section">E.10 Remote Protocol Support for Non-Stop Mode</h3>

<p><small>GDB</small>&rsquo;s remote protocol supports non-stop debugging of
multi-threaded programs, as described in <a href="Non_002dStop-Mode.html#Non_002dStop-Mode">Non-Stop Mode</a>.  If the stub
supports non-stop mode, it should report that to <small>GDB</small> by including
&lsquo;<samp>QNonStop+</samp>&rsquo; in its &lsquo;<samp>qSupported</samp>&rsquo; response (see <a href="General-Query-Packets.html#qSupported">qSupported</a>).
</p>
<p><small>GDB</small> typically sends a &lsquo;<samp>QNonStop</samp>&rsquo; packet only when
establishing a new connection with the stub.  Entering non-stop mode
does not alter the state of any currently-running threads, but targets
must stop all threads in any already-attached processes when entering
all-stop mode.  <small>GDB</small> uses the &lsquo;<samp>?</samp>&rsquo; packet as necessary to
probe the target state after a mode change.
</p>
<p>In non-stop mode, when an attached process encounters an event that
would otherwise be reported with a stop reply, it uses the
asynchronous notification mechanism (see <a href="Notification-Packets.html#Notification-Packets">Notification Packets</a>) to
inform <small>GDB</small>.  In contrast to all-stop mode, where all threads
in all processes are stopped when a stop reply is sent, in non-stop
mode only the thread reporting the stop event is stopped.  That is,
when reporting a &lsquo;<samp>S</samp>&rsquo; or &lsquo;<samp>T</samp>&rsquo; response to indicate completion
of a step operation, hitting a breakpoint, or a fault, only the
affected thread is stopped; any other still-running threads continue
to run.  When reporting a &lsquo;<samp>W</samp>&rsquo; or &lsquo;<samp>X</samp>&rsquo; response, all running
threads belonging to other attached processes continue to run.
</p>
<p>In non-stop mode, the target shall respond to the &lsquo;<samp>?</samp>&rsquo; packet as
follows.  First, any incomplete stop reply notification/&lsquo;<samp>vStopped</samp>&rsquo; 
sequence in progress is abandoned.  The target must begin a new
sequence reporting stop events for all stopped threads, whether or not
it has previously reported those events to <small>GDB</small>.  The first
stop reply is sent as a synchronous reply to the &lsquo;<samp>?</samp>&rsquo; packet, and
subsequent stop replies are sent as responses to &lsquo;<samp>vStopped</samp>&rsquo; packets
using the mechanism described above.  The target must not send
asynchronous stop reply notifications until the sequence is complete.
If all threads are running when the target receives the &lsquo;<samp>?</samp>&rsquo; packet,
or if the target is not attached to any process, it shall respond
&lsquo;<samp>OK</samp>&rsquo;.
</p>
<p>If the stub supports non-stop mode, it should also support the
&lsquo;<samp>swbreak</samp>&rsquo; stop reason if software breakpoints are supported, and
the &lsquo;<samp>hwbreak</samp>&rsquo; stop reason if hardware breakpoints are supported
(see <a href="Stop-Reply-Packets.html#swbreak-stop-reason">swbreak stop reason</a>).  This is because given the asynchronous
nature of non-stop mode, between the time a thread hits a breakpoint
and the time the event is finally processed by <small>GDB</small>, the
breakpoint may have already been removed from the target.  Due to
this, <small>GDB</small> needs to be able to tell whether a trap stop was
caused by a delayed breakpoint event, which should be ignored, as
opposed to a random trap signal, which should be reported to the user.
Note the &lsquo;<samp>swbreak</samp>&rsquo; feature implies that the target is responsible
for adjusting the PC when a software breakpoint triggers, if
necessary, such as on the x86 architecture.
</p>
<hr>
<div class="header">
<p>
Next: <a href="Packet-Acknowledgment.html#Packet-Acknowledgment" accesskey="n" rel="next">Packet Acknowledgment</a>, Previous: <a href="Notification-Packets.html#Notification-Packets" accesskey="p" rel="prev">Notification Packets</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>


</body>
</html>