view src/core/ngx_rwlock.c @ 7726:559d19037984

Limit req: unlocking of nodes on complex value errors. Previously, if there were multiple limits configured, errors in ngx_http_complex_value() during processing of a non-first limit resulted in reference count leak in shared memory nodes of already processed limits. Fix is to explicity unlock relevant nodes, much like we do when rejecting requests.
author Maxim Dounin <mdounin@mdounin.ru>
date Thu, 08 Oct 2020 17:44:34 +0300
parents d1816a2696de
children 7752d8523066
line wrap: on
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/*
 * Copyright (C) Ruslan Ermilov
 * Copyright (C) Nginx, Inc.
 */


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


#if (NGX_HAVE_ATOMIC_OPS)


#define NGX_RWLOCK_SPIN   2048
#define NGX_RWLOCK_WLOCK  ((ngx_atomic_uint_t) -1)


void
ngx_rwlock_wlock(ngx_atomic_t *lock)
{
    ngx_uint_t  i, n;

    for ( ;; ) {

        if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) {
            return;
        }

        if (ngx_ncpu > 1) {

            for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) {

                for (i = 0; i < n; i++) {
                    ngx_cpu_pause();
                }

                if (*lock == 0
                    && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK))
                {
                    return;
                }
            }
        }

        ngx_sched_yield();
    }
}


void
ngx_rwlock_rlock(ngx_atomic_t *lock)
{
    ngx_uint_t         i, n;
    ngx_atomic_uint_t  readers;

    for ( ;; ) {
        readers = *lock;

        if (readers != NGX_RWLOCK_WLOCK
            && ngx_atomic_cmp_set(lock, readers, readers + 1))
        {
            return;
        }

        if (ngx_ncpu > 1) {

            for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) {

                for (i = 0; i < n; i++) {
                    ngx_cpu_pause();
                }

                readers = *lock;

                if (readers != NGX_RWLOCK_WLOCK
                    && ngx_atomic_cmp_set(lock, readers, readers + 1))
                {
                    return;
                }
            }
        }

        ngx_sched_yield();
    }
}


void
ngx_rwlock_unlock(ngx_atomic_t *lock)
{
    ngx_atomic_uint_t  readers;

    readers = *lock;

    if (readers == NGX_RWLOCK_WLOCK) {
        (void) ngx_atomic_cmp_set(lock, NGX_RWLOCK_WLOCK, 0);
        return;
    }

    for ( ;; ) {

        if (ngx_atomic_cmp_set(lock, readers, readers - 1)) {
            return;
        }

        readers = *lock;
    }
}


void
ngx_rwlock_downgrade(ngx_atomic_t *lock)
{
    if (*lock == NGX_RWLOCK_WLOCK) {
        *lock = 1;
    }
}


#else

#if (NGX_HTTP_UPSTREAM_ZONE || NGX_STREAM_UPSTREAM_ZONE)

#error ngx_atomic_cmp_set() is not defined!

#endif

#endif