d7e793a411
mysql_backend.c:don't write to session->client if session->client is NULL mysql_common.c:assert if called with dcb==NULL
385 lines
13 KiB
C
385 lines
13 KiB
C
/*
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* This file is distributed as part of the SkySQL Gateway. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright SkySQL Ab 2013
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*/
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <sys/epoll.h>
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#include <errno.h>
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#include <poll.h>
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#include <dcb.h>
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#include <atomic.h>
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#include <gwbitmask.h>
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#include <skygw_utils.h>
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#include <log_manager.h>
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/**
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* @file poll.c - Abstraction of the epoll functionality
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 19/06/13 Mark Riddoch Initial implementation
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* 28/06/13 Mark Riddoch Added poll mask support and DCB
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* zombie management
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*
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* @endverbatim
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*/
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static int epoll_fd = -1; /**< The epoll file descriptor */
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static int shutdown = 0; /**< Flag the shutdown of the poll subsystem */
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static GWBITMASK poll_mask;
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static simple_mutex_t epoll_wait_mutex; /**< serializes calls to epoll_wait */
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/**
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* The polling statistics
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*/
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static struct {
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int n_read; /**< Number of read events */
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int n_write; /**< Number of write events */
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int n_error; /**< Number of error events */
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int n_hup; /**< Number of hangup events */
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int n_accept; /**< Number of accept events */
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int n_polls; /**< Number of poll cycles */
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} pollStats;
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/**
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* Initialise the polling system we are using for the gateway.
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*
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* In this case we are using the Linux epoll mechanism
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*/
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void
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poll_init()
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{
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if (epoll_fd != -1)
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return;
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if ((epoll_fd = epoll_create(MAX_EVENTS)) == -1)
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{
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perror("epoll_create");
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exit(-1);
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}
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memset(&pollStats, 0, sizeof(pollStats));
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bitmask_init(&poll_mask);
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simple_mutex_init(&epoll_wait_mutex, "epoll_wait_mutex");
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}
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/**
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* Add a DCB to the set of descriptors within the polling
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* environment.
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*
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* @param dcb The descriptor to add to the poll
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* @return -1 on error or 0 on success
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*/
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int
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poll_add_dcb(DCB *dcb)
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{
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int rc;
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dcb_state_t old_state = DCB_STATE_UNDEFINED;
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struct epoll_event ev;
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ev.events = EPOLLIN | EPOLLOUT | EPOLLET;
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ev.data.ptr = dcb;
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/**
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* Service listeners have different state than
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* DCBs serving client requests.
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*/
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if (dcb->dcb_role == DCB_ROLE_SERVICE_LISTENER) {
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dcb_set_state(dcb, DCB_STATE_LISTENING, &old_state);
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} else if (dcb->dcb_role == DCB_ROLE_REQUEST_HANDLER) {
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dcb_set_state(dcb, DCB_STATE_POLLING, &old_state);
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}
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rc = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, dcb->fd, &ev);
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if (rc != 0) {
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dcb_set_state(dcb, old_state, NULL);
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}
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return rc;
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}
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/**
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* Remove a descriptor from the set of descriptors within the
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* polling environment.
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*
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* @param dcb The descriptor to remove
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* @return -1 on error or 0 on success
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*/
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int
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poll_remove_dcb(DCB *dcb)
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{
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struct epoll_event ev;
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int rc;
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rc = epoll_ctl(epoll_fd, EPOLL_CTL_DEL, dcb->fd, &ev);
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if (rc == 0) {
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu [poll_remove_dcb] Removed dcb %p in state %s from "
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"poll set.",
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pthread_self(),
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dcb,
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STRDCBSTATE(dcb->state));
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} else {
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int eno = errno;
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errno = 0;
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu [poll_remove_dcb] Removing dcb %p in state %s from "
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"poll set failed due %d %s.",
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pthread_self(),
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dcb,
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STRDCBSTATE(dcb->state),
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eno,
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strerror(eno));
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}
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return rc;
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}
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#define BLOCKINGPOLL 0 /* Set BLOCKING POLL to 1 if using a single thread and to make
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* debugging easier.
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*/
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/**
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* The main polling loop
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*
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* This routine does the polling and despatches of IO events
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* to the DCB's. It may be called either directly or as the entry point
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* of a polling thread within the gateway.
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*
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* The routine will loop as long as the variable "shutdown" is set to zero,
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* setting this to a non-zero value will cause the polling loop to return.
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*
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* There are two options for the polling, a debug option that is only useful if
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* you have a single thread. This blocks in epoll_wait until an event occurs.
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*
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* The non-debug option does an epoll with a time out. This allows the checking of
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* shutdown value to be checked in all threads. The algorithm for polling in this
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* mode is to do a poll with no-wait, if no events are detected then the poll is
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* repeated with a time out. This allows for a quick check before making the call
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* with timeout. The call with the timeout differs in that the Linux scheduler may
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* deschedule a process if a timeout is included, but will not do this if a 0 timeout
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* value is given. this improves performance when the gateway is under heavy load.
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*
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* @param arg The thread ID passed as a void * to satisfy the threading package
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*/
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void
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poll_waitevents(void *arg)
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{
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struct epoll_event events[MAX_EVENTS];
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int i, nfds;
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int thread_id = (int)arg;
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bool no_op = FALSE;
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/* Add this thread to the bitmask of running polling threads */
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bitmask_set(&poll_mask, thread_id);
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while (1)
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{
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#if BLOCKINGPOLL
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if ((nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, -1)) == -1)
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{
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}
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#else
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if (!no_op) {
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skygw_log_write(LOGFILE_TRACE,
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"%lu [poll_waitevents] MaxScale thread %d > "
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"epoll_wait <",
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pthread_self(),
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thread_id);
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no_op = TRUE;
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}
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simple_mutex_lock(&epoll_wait_mutex, TRUE);
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if ((nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, 0)) == -1)
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{
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int eno = errno;
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errno = 0;
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skygw_log_write(LOGFILE_TRACE,
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"%lu [poll_waitevents] epoll_wait returned "
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"%d, errno %d",
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pthread_self(),
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nfds,
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eno);
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no_op = FALSE;
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}
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else if (nfds == 0)
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{
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nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, EPOLL_TIMEOUT);
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if (nfds == -1)
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{
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}
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}
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simple_mutex_unlock(&epoll_wait_mutex);
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#endif
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if (nfds > 0)
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{
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu [poll_waitevents] epoll_wait found %d fds",
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pthread_self(),
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nfds);
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atomic_add(&pollStats.n_polls, 1);
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for (i = 0; i < nfds; i++)
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{
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DCB *dcb = (DCB *)events[i].data.ptr;
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__uint32_t ev = events[i].events;
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CHK_DCB(dcb);
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ss_debug(spinlock_acquire(&dcb->dcb_initlock);)
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ss_dassert(dcb->state != DCB_STATE_ALLOC);
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ss_dassert(dcb->state != DCB_STATE_DISCONNECTED);
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ss_dassert(dcb->state != DCB_STATE_FREED);
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ss_debug(spinlock_release(&dcb->dcb_initlock);)
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu %d [poll_waitevents] event %d dcb %p",
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pthread_self(),
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thread_id,
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ev,
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dcb);
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if (ev & EPOLLERR)
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{
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atomic_add(&pollStats.n_error, 1);
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dcb->func.error(dcb);
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if (DCB_ISZOMBIE(dcb)) {
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continue;
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}
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}
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if (ev & EPOLLHUP)
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{
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atomic_add(&pollStats.n_hup, 1);
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dcb->func.hangup(dcb);
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if (DCB_ISZOMBIE(dcb)) {
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continue;
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}
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}
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if (ev & EPOLLOUT)
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{
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simple_mutex_lock(&dcb->dcb_write_lock,
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true);
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ss_info_dassert(!dcb->dcb_write_active,
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"Write already active");
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dcb->dcb_write_active = TRUE;
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu %d [poll_waitevents] "
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"Write in fd %d",
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pthread_self(),
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thread_id,
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dcb->fd);
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atomic_add(&pollStats.n_write, 1);
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dcb->func.write_ready(dcb);
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dcb->dcb_write_active = FALSE;
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simple_mutex_unlock(&dcb->dcb_write_lock);
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}
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if (ev & EPOLLIN)
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{
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simple_mutex_lock(&dcb->dcb_read_lock,
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true);
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ss_info_dassert(!dcb->dcb_read_active,
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"Read already active");
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dcb->dcb_read_active = TRUE;
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if (dcb->state == DCB_STATE_LISTENING)
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{
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu %d [poll_waitevents] "
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"Accept in fd %d",
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pthread_self(),
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thread_id,
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dcb->fd);
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atomic_add(&pollStats.n_accept, 1);
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dcb->func.accept(dcb);
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}
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else
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{
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skygw_log_write(
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LOGFILE_TRACE,
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"%lu %d [poll_waitevents] "
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"Read in fd %d",
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pthread_self(),
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thread_id,
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dcb->fd);
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atomic_add(&pollStats.n_read, 1);
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dcb->func.read(dcb);
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}
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dcb->dcb_read_active = FALSE;
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simple_mutex_unlock(
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&dcb->dcb_read_lock);
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}
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} /**< for */
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no_op = FALSE;
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}
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dcb_process_zombies(thread_id);
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if (shutdown)
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{
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/**
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* Remove this thread from the bitmask of running
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* polling threads
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*/
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bitmask_clear(&poll_mask, thread_id);
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return;
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}
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} /**< while(1) */
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}
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/**
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* Shutdown the polling loop
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*/
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void
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poll_shutdown()
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{
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shutdown = 1;
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}
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/**
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* Return the bitmask of polling threads
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*
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* @return The bitmask of the running polling threads
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*/
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GWBITMASK *
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poll_bitmask()
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{
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return &poll_mask;
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}
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/**
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* Debug routine to print the polling statistics
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*
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* @param dcb DCB to print to
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*/
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void
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dprintPollStats(DCB *dcb)
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{
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dcb_printf(dcb, "Number of epoll cycles: %d\n", pollStats.n_polls);
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dcb_printf(dcb, "Number of read events: %d\n", pollStats.n_read);
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dcb_printf(dcb, "Number of write events: %d\n", pollStats.n_write);
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dcb_printf(dcb, "Number of error events: %d\n", pollStats.n_error);
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dcb_printf(dcb, "Number of hangup events: %d\n", pollStats.n_hup);
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dcb_printf(dcb, "Number of accept events: %d\n", pollStats.n_accept);
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}
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