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| <a name="Interrupts"></a> |
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| Next: <a href="Notification-Packets.html#Notification-Packets" accesskey="n" rel="next">Notification Packets</a>, Previous: <a href="Host-I_002fO-Packets.html#Host-I_002fO-Packets" accesskey="p" rel="prev">Host I/O 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> |
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| <a name="Interrupts-1"></a> |
| <h3 class="section">E.8 Interrupts</h3> |
| <a name="index-interrupts-_0028remote-protocol_0029"></a> |
| |
| <p>When a program on the remote target is running, <small>GDB</small> may |
| attempt to interrupt it by sending a ‘<samp>Ctrl-C</samp>’, <code>BREAK</code> or |
| a <code>BREAK</code> followed by <code>g</code>, |
| control of which is specified via <small>GDB</small>’s ‘<samp>interrupt-sequence</samp>’. |
| </p> |
| <p>The precise meaning of <code>BREAK</code> is defined by the transport |
| mechanism and may, in fact, be undefined. <small>GDB</small> does not |
| currently define a <code>BREAK</code> mechanism for any of the network |
| interfaces except for TCP, in which case <small>GDB</small> sends the |
| <code>telnet</code> BREAK sequence. |
| </p> |
| <p>‘<samp>Ctrl-C</samp>’, on the other hand, is defined and implemented for all |
| transport mechanisms. It is represented by sending the single byte |
| <code>0x03</code> without any of the usual packet overhead described in |
| the Overview section (see <a href="Overview.html#Overview">Overview</a>). When a <code>0x03</code> byte is |
| transmitted as part of a packet, it is considered to be packet data |
| and does <em>not</em> represent an interrupt. E.g., an ‘<samp>X</samp>’ packet |
| (see <a href="Packets.html#X-packet">X packet</a>), used for binary downloads, may include an unescaped |
| <code>0x03</code> as part of its packet. |
| </p> |
| <p><code>BREAK</code> followed by <code>g</code> is also known as Magic SysRq g. |
| When Linux kernel receives this sequence from serial port, |
| it stops execution and connects to gdb. |
| </p> |
| <p>Stubs are not required to recognize these interrupt mechanisms and the |
| precise meaning associated with receipt of the interrupt is |
| implementation defined. If the target supports debugging of multiple |
| threads and/or processes, it should attempt to interrupt all |
| currently-executing threads and processes. |
| If the stub is successful at interrupting the |
| running program, it should send one of the stop |
| reply packets (see <a href="Stop-Reply-Packets.html#Stop-Reply-Packets">Stop Reply Packets</a>) to <small>GDB</small> as a result |
| of successfully stopping the program in all-stop mode, and a stop reply |
| for each stopped thread in non-stop mode. |
| Interrupts received while the |
| program is stopped are discarded. |
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