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.


CFLAGS = -zq -bt=nt -ot -op -oi -oe -s -bm $(CPU_OPT)

zlib.lib:
	cd $(ZLIB)

	wcl386 -c $(CFLAGS) adler32.c crc32.c deflate.c trees.c zutil.c &
		compress.c inflate.c inffast.c inftrees.c
	wlib -n zlib.lib adler32.obj crc32.obj deflate.obj trees.obj &
		zutil.obj compress.obj inflate.obj inffast.obj inftrees.obj