| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- Copyright (C) 1988-2015 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 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>Debugging with GDB: Remote Non-Stop</title> |
| |
| <meta name="description" content="Debugging with GDB: Remote Non-Stop"> |
| <meta name="keywords" content="Debugging with GDB: Remote Non-Stop"> |
| <meta name="resource-type" content="document"> |
| <meta name="distribution" content="global"> |
| <meta name="Generator" content="makeinfo"> |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> |
| <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.smallquotation {font-size: smaller} |
| div.display {margin-left: 3.2em} |
| div.example {margin-left: 3.2em} |
| div.indentedblock {margin-left: 3.2em} |
| div.lisp {margin-left: 3.2em} |
| div.smalldisplay {margin-left: 3.2em} |
| div.smallexample {margin-left: 3.2em} |
| div.smallindentedblock {margin-left: 3.2em; font-size: smaller} |
| 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.nocodebreak {white-space:nowrap} |
| span.nolinebreak {white-space:nowrap} |
| span.roman {font-family:serif; font-weight:normal} |
| span.sansserif {font-family:sans-serif; font-weight:normal} |
| ul.no-bullet {list-style: none} |
| --> |
| </style> |
| |
| |
| </head> |
| |
| <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> |
| <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> [<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>’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 |
| ‘<samp>QNonStop+</samp>’ in its ‘<samp>qSupported</samp>’ response (see <a href="General-Query-Packets.html#qSupported">qSupported</a>). |
| </p> |
| <p><small>GDB</small> typically sends a ‘<samp>QNonStop</samp>’ 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 ‘<samp>?</samp>’ 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 ‘<samp>S</samp>’ or ‘<samp>T</samp>’ 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 ‘<samp>W</samp>’ or ‘<samp>X</samp>’ response, all running |
| threads belonging to other attached processes continue to run. |
| </p> |
| <p>In non-stop mode, the target shall respond to the ‘<samp>?</samp>’ packet as |
| follows. First, any incomplete stop reply notification/‘<samp>vStopped</samp>’ |
| 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 ‘<samp>?</samp>’ packet, and |
| subsequent stop replies are sent as responses to ‘<samp>vStopped</samp>’ 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 ‘<samp>?</samp>’ packet, |
| or if the target is not attached to any process, it shall respond |
| ‘<samp>OK</samp>’. |
| </p> |
| <p>If the stub supports non-stop mode, it should also support the |
| ‘<samp>swbreak</samp>’ stop reason if software breakpoints are supported, and |
| the ‘<samp>hwbreak</samp>’ 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 ‘<samp>swbreak</samp>’ 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> [<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> |
