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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gdb/Interrupted-System-Calls.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
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diff --git a/share/doc/gdb/Interrupted-System-Calls.html b/share/doc/gdb/Interrupted-System-Calls.html new file mode 100644 index 0000000..0af6863 --- /dev/null +++ b/share/doc/gdb/Interrupted-System-Calls.html @@ -0,0 +1,119 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 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 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Interrupted System Calls</title> + +<meta name="description" content="Debugging with GDB: Interrupted System Calls"> +<meta name="keywords" content="Debugging with GDB: Interrupted System Calls"> +<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="Thread-Stops.html#Thread-Stops" rel="up" title="Thread Stops"> +<link href="Observer-Mode.html#Observer-Mode" rel="next" title="Observer Mode"> +<link href="Thread_002dSpecific-Breakpoints.html#Thread_002dSpecific-Breakpoints" rel="previous" title="Thread-Specific Breakpoints"> +<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="Interrupted-System-Calls"></a> +<div class="header"> +<p> +Next: <a href="Observer-Mode.html#Observer-Mode" accesskey="n" rel="next">Observer Mode</a>, Previous: <a href="Thread_002dSpecific-Breakpoints.html#Thread_002dSpecific-Breakpoints" accesskey="p" rel="previous">Thread-Specific Breakpoints</a>, Up: <a href="Thread-Stops.html#Thread-Stops" accesskey="u" rel="up">Thread Stops</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="Interrupted-System-Calls-1"></a> +<h4 class="subsection">5.5.5 Interrupted System Calls</h4> + +<a name="index-thread-breakpoints-and-system-calls"></a> +<a name="index-system-calls-and-thread-breakpoints"></a> +<a name="index-premature-return-from-system-calls"></a> +<p>There is an unfortunate side effect when using <small>GDB</small> to debug +multi-threaded programs. If one thread stops for a +breakpoint, or for some other reason, and another thread is blocked in a +system call, then the system call may return prematurely. This is a +consequence of the interaction between multiple threads and the signals +that <small>GDB</small> uses to implement breakpoints and other events that +stop execution. +</p> +<p>To handle this problem, your program should check the return value of +each system call and react appropriately. This is good programming +style anyways. +</p> +<p>For example, do not write code like this: +</p> +<div class="smallexample"> +<pre class="smallexample"> sleep (10); +</pre></div> + +<p>The call to <code>sleep</code> will return early if a different thread stops +at a breakpoint or for some other reason. +</p> +<p>Instead, write this: +</p> +<div class="smallexample"> +<pre class="smallexample"> int unslept = 10; + while (unslept > 0) + unslept = sleep (unslept); +</pre></div> + +<p>A system call is allowed to return early, so the system is still +conforming to its specification. But <small>GDB</small> does cause your +multi-threaded program to behave differently than it would without +<small>GDB</small>. +</p> +<p>Also, <small>GDB</small> uses internal breakpoints in the thread library to +monitor certain events such as thread creation and thread destruction. +When such an event happens, a system call in another thread may return +prematurely, even though your program does not appear to stop. +</p> + + + +</body> +</html> |