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core: Use eventfd for alert pipes on Linux when possible
The primary win of switching to eventfd when possible is that it only uses a single file descriptor while pipe() will use two. This means for each bridge channel we're reducing the number of required file descriptors by 1, and - if you're using timerfd - we also now have 1 less file descriptor per Asterisk channel. The API is not ideal (passing int arrays), but this is the cleanest approach I could come up with to maintain API/ABI. I've also removed what I believe to be an erroneous code block that checked the non-blocking flag on the pipe ends for each read. If the file descriptor is 'losing' its non-blocking mode, it is because of a bug somewhere else in our code. In my testing I haven't seen any measurable difference in performance. Change-Id: Iff0fb1573e7f7a187d5211ddc60aa8f3da3edb1d
This commit is contained in:
Sean Bright
159
include/asterisk/alertpipe.h
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159
include/asterisk/alertpipe.h
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@@ -0,0 +1,159 @@
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/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2017, Sean Bright
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*
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* Sean Bright <sean.bright@gmail.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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#ifndef ASTERISK_ALERTPIPE_H
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#define ASTERISK_ALERTPIPE_H
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#include "asterisk/utils.h"
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typedef enum {
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AST_ALERT_READ_SUCCESS = 0,
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AST_ALERT_NOT_READABLE,
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AST_ALERT_READ_FAIL,
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AST_ALERT_READ_FATAL,
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} ast_alert_status_t;
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/*!
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* \brief Initialize an alert pipe
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* \since 13.16.0
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*
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* \param p a two-element array to hold the alert pipe's file descriptors
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*
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* \return non-zero if a failure occurred, zero otherwise.
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*/
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int ast_alertpipe_init(int alert_pipe[2]);
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/*!
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* \brief Close an alert pipe
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* \since 13.16.0
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*
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* \param p a two-element containing the alert pipe's file descriptors
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*/
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void ast_alertpipe_close(int alert_pipe[2]);
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/*!
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* \brief Read an event from an alert pipe
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*
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* \retval AST_ALERT_READ_SUCCESS on success
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* \retval AST_ALERT_NOT_READABLE if the alert pipe is not readable
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* \retval AST_ALERT_READ_FATAL if the alert pipe's file descriptors are in
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* blocking mode, or a read error occurs.
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*/
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ast_alert_status_t ast_alertpipe_read(int alert_pipe[2]);
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/*!
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* \brief Write an event to an alert pipe
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*
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* \return see write(2)
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*/
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ssize_t ast_alertpipe_write(int alert_pipe[2]);
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/*!
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* \brief Consume all alerts written to the alert pipe
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*
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* \retval AST_ALERT_READ_SUCCESS on success
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* \retval AST_ALERT_NOT_READABLE if the alert pipe is not readable
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* \retval AST_ALERT_READ_FATAL if the alert pipe's file descriptors are in
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* blocking mode, or a read error occurs.
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*/
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ast_alert_status_t ast_alertpipe_flush(int alert_pipe[2]);
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/*!
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* \brief Sets the alert pipe file descriptors to default values
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*/
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AST_INLINE_API(
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void ast_alertpipe_clear(int alert_pipe[2]),
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{
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alert_pipe[0] = alert_pipe[1] = -1;
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}
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)
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/*!
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* \brief Determine if the alert pipe is readable
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*
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* \return non-zero if the alert pipe is readable, zero otherwise.
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*/
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AST_INLINE_API(
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int attribute_pure ast_alertpipe_readable(int alert_pipe[2]),
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{
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return alert_pipe[0] > -1;
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}
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)
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/*!
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* \brief Determine if the alert pipe is writable
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*
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* \return non-zero if the alert pipe is writable, zero otherwise.
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*/
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AST_INLINE_API(
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int attribute_pure ast_alertpipe_writable(int alert_pipe[2]),
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{
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return alert_pipe[1] > -1;
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}
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)
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/*!
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* \brief Get the alert pipe's read file descriptor
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* \since 13.16.0
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*
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* \param p a two-element array containing the alert pipe's file descriptors
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*
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* \return -1 if the file descriptor is not initialized, a non-negative value
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* otherwise.
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*/
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AST_INLINE_API(
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int attribute_pure ast_alertpipe_readfd(int alert_pipe[2]),
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{
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return alert_pipe[0];
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}
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)
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/*!
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* \brief Swap the file descriptors from two alert pipes
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* \since 13.16.0
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*
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* \param p1 a two-element array containing an alert pipe's file descriptors
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* \param p2 a two-element array containing an alert pipe's file descriptors
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*/
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AST_INLINE_API(
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void ast_alertpipe_swap(int alert_pipe_1[2], int alert_pipe_2[2]),
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{
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SWAP(alert_pipe_1[0], alert_pipe_2[0]);
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SWAP(alert_pipe_1[1], alert_pipe_2[1]);
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}
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)
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#endif /* ASTERISK_ALERTPIPE_H */
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@@ -225,6 +225,10 @@
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/* Define to 1 if you have the `euidaccess' function. */
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#undef HAVE_EUIDACCESS
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/* Define to 1 if your system supports eventfd and the EFD_NONBLOCK and
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EFD_SEMAPHORE flags. */
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#undef HAVE_EVENTFD
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/* Define to 1 if you have the `exp' function. */
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#undef HAVE_EXP
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@@ -123,6 +123,7 @@ References:
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#ifndef _ASTERISK_CHANNEL_H
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#define _ASTERISK_CHANNEL_H
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#include "asterisk/alertpipe.h"
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#include "asterisk/abstract_jb.h"
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#include "asterisk/astobj2.h"
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#include "asterisk/poll-compat.h"
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@@ -4267,12 +4268,6 @@ struct ast_namedgroups *ast_channel_named_pickupgroups(const struct ast_channel
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void ast_channel_named_pickupgroups_set(struct ast_channel *chan, struct ast_namedgroups *value);
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/* Alertpipe accessors--the "internal" functions for channel.c use only */
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typedef enum {
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AST_ALERT_READ_SUCCESS = 0,
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AST_ALERT_NOT_READABLE,
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AST_ALERT_READ_FAIL,
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AST_ALERT_READ_FATAL,
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} ast_alert_status_t;
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int ast_channel_alert_write(struct ast_channel *chan);
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int ast_channel_alert_writable(struct ast_channel *chan);
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ast_alert_status_t ast_channel_internal_alert_flush(struct ast_channel *chan);
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