diff options
Diffstat (limited to 'share/doc/gdb/All_002dStop-Mode.html')
| -rw-r--r-- | share/doc/gdb/All_002dStop-Mode.html | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/share/doc/gdb/All_002dStop-Mode.html b/share/doc/gdb/All_002dStop-Mode.html new file mode 100644 index 0000000..1e595c2 --- /dev/null +++ b/share/doc/gdb/All_002dStop-Mode.html @@ -0,0 +1,195 @@ +<!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: All-Stop Mode</title> + +<meta name="description" content="Debugging with GDB: All-Stop Mode"> +<meta name="keywords" content="Debugging with GDB: All-Stop Mode"> +<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="Non_002dStop-Mode.html#Non_002dStop-Mode" rel="next" title="Non-Stop Mode"> +<link href="Thread-Stops.html#Thread-Stops" rel="previous" title="Thread Stops"> +<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="All_002dStop-Mode"></a> +<div class="header"> +<p> +Next: <a href="Non_002dStop-Mode.html#Non_002dStop-Mode" accesskey="n" rel="next">Non-Stop Mode</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="All_002dStop-Mode-1"></a> +<h4 class="subsection">5.5.1 All-Stop Mode</h4> + +<a name="index-all_002dstop-mode"></a> + +<p>In all-stop mode, whenever your program stops under <small>GDB</small> for any reason, +<em>all</em> threads of execution stop, not just the current thread. This +allows you to examine the overall state of the program, including +switching between threads, without worrying that things may change +underfoot. +</p> +<p>Conversely, whenever you restart the program, <em>all</em> threads start +executing. <em>This is true even when single-stepping</em> with commands +like <code>step</code> or <code>next</code>. +</p> +<p>In particular, <small>GDB</small> cannot single-step all threads in lockstep. +Since thread scheduling is up to your debugging target’s operating +system (not controlled by <small>GDB</small>), other threads may +execute more than one statement while the current thread completes a +single step. Moreover, in general other threads stop in the middle of a +statement, rather than at a clean statement boundary, when the program +stops. +</p> +<p>You might even find your program stopped in another thread after +continuing or even single-stepping. This happens whenever some other +thread runs into a breakpoint, a signal, or an exception before the +first thread completes whatever you requested. +</p> +<a name="index-automatic-thread-selection"></a> +<a name="index-switching-threads-automatically"></a> +<a name="index-threads_002c-automatic-switching"></a> +<p>Whenever <small>GDB</small> stops your program, due to a breakpoint or a +signal, it automatically selects the thread where that breakpoint or +signal happened. <small>GDB</small> alerts you to the context switch with a +message such as ‘<samp>[Switching to Thread <var>n</var>]</samp>’ to identify the +thread. +</p> +<p>On some OSes, you can modify <small>GDB</small>’s default behavior by +locking the OS scheduler to allow only a single thread to run. +</p> +<dl compact="compact"> +<dt><code>set scheduler-locking <var>mode</var></code></dt> +<dd><a name="index-scheduler-locking-mode"></a> +<a name="index-lock-scheduler"></a> +<p>Set the scheduler locking mode. It applies to normal execution, +record mode, and replay mode. <var>mode</var> can be one of +the following: +</p> +<dl compact="compact"> +<dt><code>off</code></dt> +<dd><p>There is no locking and any thread may run at any time. +</p> +</dd> +<dt><code>on</code></dt> +<dd><p>Only the current thread may run when the inferior is resumed. +</p> +</dd> +<dt><code>step</code></dt> +<dd><p>Behaves like <code>on</code> when stepping, and <code>off</code> otherwise. +Threads other than the current never get a chance to run when you +step, and they are completely free to run when you use commands like +‘<samp>continue</samp>’, ‘<samp>until</samp>’, or ‘<samp>finish</samp>’. +</p> +<p>This mode optimizes for single-stepping; it prevents other threads +from preempting the current thread while you are stepping, so that the +focus of debugging does not change unexpectedly. However, unless +another thread hits a breakpoint during its timeslice, <small>GDB</small> +does not change the current thread away from the thread that you are +debugging. +</p> +</dd> +<dt><code>replay</code></dt> +<dd><p>Behaves like <code>on</code> in replay mode, and <code>off</code> in either record +mode or during normal execution. This is the default mode. +</p></dd> +</dl> + +</dd> +<dt><code>show scheduler-locking</code></dt> +<dd><p>Display the current scheduler locking mode. +</p></dd> +</dl> + +<a name="index-resume-threads-of-multiple-processes-simultaneously"></a> +<p>By default, when you issue one of the execution commands such as +<code>continue</code>, <code>next</code> or <code>step</code>, <small>GDB</small> allows only +threads of the current inferior to run. For example, if <small>GDB</small> +is attached to two inferiors, each with two threads, the +<code>continue</code> command resumes only the two threads of the current +inferior. This is useful, for example, when you debug a program that +forks and you want to hold the parent stopped (so that, for instance, +it doesn’t run to exit), while you debug the child. In other +situations, you may not be interested in inspecting the current state +of any of the processes <small>GDB</small> is attached to, and you may want +to resume them all until some breakpoint is hit. In the latter case, +you can instruct <small>GDB</small> to allow all threads of all the +inferiors to run with the <code>set <span class="nolinebreak">schedule-multiple</span></code><!-- /@w --> command. +</p> +<dl compact="compact"> +<dd><a name="index-set-schedule_002dmultiple"></a> +</dd> +<dt><code>set schedule-multiple</code></dt> +<dd><p>Set the mode for allowing threads of multiple processes to be resumed +when an execution command is issued. When <code>on</code>, all threads of +all processes are allowed to run. When <code>off</code>, only the threads +of the current process are resumed. The default is <code>off</code>. The +<code>scheduler-locking</code> mode takes precedence when set to <code>on</code>, +or while you are stepping and set to <code>step</code>. +</p> +</dd> +<dt><code>show schedule-multiple</code></dt> +<dd><p>Display the current mode for resuming the execution of threads of +multiple processes. +</p></dd> +</dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Non_002dStop-Mode.html#Non_002dStop-Mode" accesskey="n" rel="next">Non-Stop Mode</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> + + + +</body> +</html> |