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c-ares/docs/ares_threadsafety.3

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Basic Thread Safety (#636) c-ares does not have any concept of thread-safety. It has always been 100% up to the implementor to ensure they never call c-ares from more than one thread at a time. This patch adds basic thread-safety support, which can be disabled at compile time if not desired. It uses a single recursive mutex per channel, which should be extremely quick when uncontested so overhead should be minimal. Fixes Bug: #610 Also sets the stage to implement #611 Fix By: Brad House (@bradh352)
1 year ago
.\"
.\" SPDX-License-Identifier: MIT
.\"
Add ares_queue_wait_empty() for use with EventThreads (#710) It may be useful to wait for the queue to be empty under certain conditions (mainly test cases), expose a function to efficiently do this and rework test cases to use it. Fix By: Brad House (@bradh352)
10 months ago
.TH ARES_THREADSAFETY 3 "26 November 2023"
Basic Thread Safety (#636) c-ares does not have any concept of thread-safety. It has always been 100% up to the implementor to ensure they never call c-ares from more than one thread at a time. This patch adds basic thread-safety support, which can be disabled at compile time if not desired. It uses a single recursive mutex per channel, which should be extremely quick when uncontested so overhead should be minimal. Fixes Bug: #610 Also sets the stage to implement #611 Fix By: Brad House (@bradh352)
1 year ago
.SH NAME
ares_threadsafety \- Query if c-ares was built with thread-safety
.SH SYNOPSIS
.nf
#include <ares.h>
ares_bool_t ares_threadsafety(void);
.fi
.SH DESCRIPTION
The \fBares_threadsafety(3)\fP function returns if the library was built with
thread safety enabled or not.
As of c-ares 1.23.0, this simply means that every public function which
references an \fIares_channel_t\fP object will lock the channel on entry and
remove a simply
1 year ago
release the lock on exit of the function. This will prevent concurrent
Event Subsystem: No longer require integrators to have their own (#696) This PR implements an event thread to process all events on file descriptors registered by c-ares. Prior to this feature, integrators were required to understand the internals of c-ares and how to monitor file descriptors and timeouts and process events. Implements OS-specific efficient polling such as epoll(), kqueue(), or IOCP, and falls back to poll() or select() if otherwise unsupported. At this point, it depends on basic threading primitives such as pthreads or windows threads. If enabled via the ARES_OPT_EVENT_THREAD option passed to ares_init_options(), then socket callbacks cannot be used. Fixes Bug: #611 Fix By: Brad House (@bradh352)
10 months ago
thread access to the channel, thus ensuring no corruption can occur.
As of c-ares 1.26.0, this also indicates if \fBARES_OPT_EVENT_THREAD\fP can
be passed to \fIares_init_options(3)\fP.
Basic Thread Safety (#636) c-ares does not have any concept of thread-safety. It has always been 100% up to the implementor to ensure they never call c-ares from more than one thread at a time. This patch adds basic thread-safety support, which can be disabled at compile time if not desired. It uses a single recursive mutex per channel, which should be extremely quick when uncontested so overhead should be minimal. Fixes Bug: #610 Also sets the stage to implement #611 Fix By: Brad House (@bradh352)
1 year ago
.SH RETURN VALUES
\fIares_threadsafety(3)\fP can return any of the following values:
.TP 14
.B ARES_TRUE
Built with thread safety.
.TP 14
.B ARES_FALSE
Built without thread safety
.TP 14
.SH AVAILABILITY
This function was first introduced in c-ares version 1.23.0.
.SH SEE ALSO
.BR ares_init (3),
.BR ares_init_options (3),
.BR ares_destroy (3),
.BR ares_dup (3),
.BR ares_library_init (3),
.BR ares_set_servers (3)