Changed ngx_chain_update_chains() to test tag first (ticket #2248). Without this change, aio used with HTTP/2 can result in connection hang, as observed with "aio threads; aio_write on;" and proxying (ticket #2248). The problem is that HTTP/2 updates buffers outside of the output filters (notably, marks them as sent), and then posts a write event to call output filters. If a filter does not call the next one for some reason (for example, because of an AIO operation in progress), this might result in a state when the owner of a buffer already called ngx_chain_update_chains() and can reuse the buffer, while the same buffer is still sitting in the busy chain of some other filter. In the particular case a buffer was sitting in output chain's ctx->busy, and was reused by event pipe. Output chain's ctx->busy was permanently blocked by it, and this resulted in connection hang. Fix is to change ngx_chain_update_chains() to skip buffers from other modules unconditionally, without trying to wait for these buffers to become empty.

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_SETPROCTITLE_H_INCLUDED_
#define _NGX_SETPROCTITLE_H_INCLUDED_


#if (NGX_HAVE_SETPROCTITLE)

/* FreeBSD, NetBSD, OpenBSD */

#define ngx_init_setproctitle(log) NGX_OK
#define ngx_setproctitle(title)    setproctitle("%s", title)


#else /* !NGX_HAVE_SETPROCTITLE */

#if !defined NGX_SETPROCTITLE_USES_ENV

#if (NGX_SOLARIS)

#define NGX_SETPROCTITLE_USES_ENV  1
#define NGX_SETPROCTITLE_PAD       ' '

ngx_int_t ngx_init_setproctitle(ngx_log_t *log);
void ngx_setproctitle(char *title);

#elif (NGX_LINUX) || (NGX_DARWIN)

#define NGX_SETPROCTITLE_USES_ENV  1
#define NGX_SETPROCTITLE_PAD       '\0'

ngx_int_t ngx_init_setproctitle(ngx_log_t *log);
void ngx_setproctitle(char *title);

#else

#define ngx_init_setproctitle(log) NGX_OK
#define ngx_setproctitle(title)

#endif /* OSes */

#endif /* NGX_SETPROCTITLE_USES_ENV */

#endif /* NGX_HAVE_SETPROCTITLE */


#endif /* _NGX_SETPROCTITLE_H_INCLUDED_ */