view src/event/ngx_event_posted.c @ 3293:8abb88374c6c

Fix a bug introduced in r2032: After a child process has read a terminate message from a channel, the process tries to read the channel again. The kernel (at least FreeBSD) may preempt the process and sends a SIGIO signal to a master process. The master process sends a new terminate message, the kernel switches again to the the child process, and the child process reads the messages instead of an EAGAIN error. And this may repeat over and over. Being that the child process can not exit the cycle and test the termination flag set by the message handler. The fix disallow the master process to send a new terminate message on SIGIO signal reception. It may send the message only on SIGALARM signal.
author Igor Sysoev <igor@sysoev.ru>
date Wed, 04 Nov 2009 19:41:08 +0000
parents 9c2f3ed7a247
children d620f497c50f
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>


ngx_thread_volatile ngx_event_t  *ngx_posted_accept_events;
ngx_thread_volatile ngx_event_t  *ngx_posted_events;

#if (NGX_THREADS)
ngx_mutex_t                      *ngx_posted_events_mutex;
#endif


void
ngx_event_process_posted(ngx_cycle_t *cycle,
    ngx_thread_volatile ngx_event_t **posted)
{
    ngx_event_t  *ev;

    for ( ;; ) {

        ev = (ngx_event_t *) *posted;

        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                      "posted event %p", ev);

        if (ev == NULL) {
            return;
        }

        ngx_delete_posted_event(ev);

        ev->handler(ev);
    }
}


#if (NGX_THREADS) && !(NGX_WIN32)

void
ngx_wakeup_worker_thread(ngx_cycle_t *cycle)
{
    ngx_int_t     i;
#if 0
    ngx_uint_t    busy;
    ngx_event_t  *ev;

    busy = 1;

    if (ngx_mutex_lock(ngx_posted_events_mutex) == NGX_ERROR) {
        return;
    }

    for (ev = (ngx_event_t *) ngx_posted_events; ev; ev = ev->next) {
        if (*(ev->lock) == 0) {
            busy = 0;
            break;
        }
    }

    ngx_mutex_unlock(ngx_posted_events_mutex);

    if (busy) {
        return;
    }
#endif

    for (i = 0; i < ngx_threads_n; i++) {
        if (ngx_threads[i].state == NGX_THREAD_FREE) {
            ngx_cond_signal(ngx_threads[i].cv);
            return;
        }
    }
}


ngx_int_t
ngx_event_thread_process_posted(ngx_cycle_t *cycle)
{
    ngx_event_t  *ev;

    for ( ;; ) {

        ev = (ngx_event_t *) ngx_posted_events;

        for ( ;; ) {

            ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                          "posted event %p", ev);

            if (ev == NULL) {
                return NGX_OK;
            }

            if (ngx_trylock(ev->lock) == 0) {

                ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                               "posted event %p is busy", ev);

                ev = ev->next;
                continue;
            }

            if (ev->lock != ev->own_lock) {
                if (*(ev->own_lock)) {
                    ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,
                             "the own lock of the posted event %p is busy", ev);
                    ngx_unlock(ev->lock);
                    ev = ev->next;
                    continue;
                }
                *(ev->own_lock) = 1;
            }

            ngx_delete_posted_event(ev);

            ev->locked = 1;

            ev->ready |= ev->posted_ready;
            ev->timedout |= ev->posted_timedout;
            ev->pending_eof |= ev->posted_eof;
#if (NGX_HAVE_KQUEUE)
            ev->kq_errno |= ev->posted_errno;
#endif
            if (ev->posted_available) {
                ev->available = ev->posted_available;
            }

            ev->posted_ready = 0;
            ev->posted_timedout = 0;
            ev->posted_eof = 0;
#if (NGX_HAVE_KQUEUE)
            ev->posted_errno = 0;
#endif
            ev->posted_available = 0;

            ngx_mutex_unlock(ngx_posted_events_mutex);

            ev->handler(ev);

            ngx_mutex_lock(ngx_posted_events_mutex);

            if (ev->locked) {
                ngx_unlock(ev->lock);

                if (ev->lock != ev->own_lock) {
                    ngx_unlock(ev->own_lock);
                }
            }

            ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                           "posted event %p is done", ev);

            break;
        }
    }
}

#else

void
ngx_wakeup_worker_thread(ngx_cycle_t *cycle)
{
}

#endif