Date: Fri, 3 Feb 2012 20:24:18 +0000 (UTC) From: Jilles Tjoelker <jilles@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r230955 - stable/9/sys/kern Message-ID: <201202032024.q13KOICY002733@svn.freebsd.org>
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Author: jilles Date: Fri Feb 3 20:24:18 2012 New Revision: 230955 URL: http://svn.freebsd.org/changeset/base/230955 Log: MFC r228510: Fix select/poll/kqueue for write on reverse direction before first write. The reverse direction of a pipe is lazily allocated on the first write in that direction (because pipes are usually used in one direction only). A special case is needed to ensure the pipe appears writable before the first write because there are 0 bytes of pending data in 0 bytes of buffer space at that point, leaving 0 bytes of data that can be written with the normal code. Note that the first write returns [ENOMEM] if kern.ipc.maxpipekva is exceeded and does not block or return [EAGAIN], so selecting true for write is correct even in that case. PR: kern/93685 Modified: stable/9/sys/kern/sys_pipe.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/kern/sys_pipe.c ============================================================================== --- stable/9/sys/kern/sys_pipe.c Fri Feb 3 20:20:30 2012 (r230954) +++ stable/9/sys/kern/sys_pipe.c Fri Feb 3 20:24:18 2012 (r230955) @@ -1349,7 +1349,8 @@ pipe_poll(fp, events, active_cred, td) if (wpipe->pipe_present != PIPE_ACTIVE || (wpipe->pipe_state & PIPE_EOF) || (((wpipe->pipe_state & PIPE_DIRECTW) == 0) && - (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF)) + ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF || + wpipe->pipe_buffer.size == 0))) revents |= events & (POLLOUT | POLLWRNORM); if ((events & POLLINIGNEOF) == 0) { @@ -1660,7 +1661,8 @@ filt_pipewrite(struct knote *kn, long hi PIPE_UNLOCK(rpipe); return (1); } - kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt; + kn->kn_data = (wpipe->pipe_buffer.size > 0) ? + (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF; if (wpipe->pipe_state & PIPE_DIRECTW) kn->kn_data = 0;
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