b738ca88a2
When my earlier MPSAFE TTY prototypes still implemented line disciplines, we needed a mechanism to abort read()'s on PTY master devices when inside the line discipline. Because this is no longer the case, these checks have become unneeded.
355 lines
9.3 KiB
C
355 lines
9.3 KiB
C
/*-
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* Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
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* All rights reserved.
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*
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* Portions of this software were developed under sponsorship from Snow
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* B.V., the Netherlands.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/queue.h>
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#include <sys/sysctl.h>
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#include <sys/systm.h>
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#include <sys/tty.h>
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#include <sys/uio.h>
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#include <vm/uma.h>
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/*
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* TTY output queue buffering.
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*
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* The previous design of the TTY layer offered the so-called clists.
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* These clists were used for both the input queues and the output
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* queue. We don't use certain features on the output side, like quoting
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* bits for parity marking and such. This mechanism is similar to the
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* old clists, but only contains the features we need to buffer the
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* output.
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*/
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/* Statistics. */
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static long ttyoutq_nfast = 0;
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SYSCTL_LONG(_kern, OID_AUTO, tty_outq_nfast, CTLFLAG_RD,
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&ttyoutq_nfast, 0, "Unbuffered reads to userspace on output");
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static long ttyoutq_nslow = 0;
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SYSCTL_LONG(_kern, OID_AUTO, tty_outq_nslow, CTLFLAG_RD,
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&ttyoutq_nslow, 0, "Buffered reads to userspace on output");
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struct ttyoutq_block {
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STAILQ_ENTRY(ttyoutq_block) tob_list;
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char tob_data[TTYOUTQ_DATASIZE];
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};
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static uma_zone_t ttyoutq_zone;
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void
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ttyoutq_flush(struct ttyoutq *to)
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{
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to->to_begin = 0;
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to->to_end = 0;
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}
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void
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ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size)
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{
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unsigned int nblocks;
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struct ttyoutq_block *tob;
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nblocks = howmany(size, TTYOUTQ_DATASIZE);
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while (nblocks > to->to_nblocks) {
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/*
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* List is getting bigger.
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* Add new blocks to the tail of the list.
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*
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* We must unlock the TTY temporarily, because we need
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* to allocate memory. This won't be a problem, because
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* in the worst case, another thread ends up here, which
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* may cause us to allocate too many blocks, but this
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* will be caught by the loop below.
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*/
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tty_unlock(tp);
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tob = uma_zalloc(ttyoutq_zone, M_WAITOK);
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tty_lock(tp);
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if (tty_gone(tp))
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return;
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STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list);
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to->to_nblocks++;
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}
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while (nblocks < to->to_nblocks) {
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/*
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* List is getting smaller. Remove unused blocks at the
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* end. This means we cannot guarantee this routine
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* shrinks buffers properly, when we need to reclaim
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* more space than there is available.
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*
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* XXX TODO: Two solutions here:
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* - Throw data away
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* - Temporarily hit the watermark until enough data has
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* been flushed, so we can remove the blocks.
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*/
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if (to->to_end == 0) {
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tob = STAILQ_FIRST(&to->to_list);
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if (tob == NULL)
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break;
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STAILQ_REMOVE_HEAD(&to->to_list, tob_list);
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} else {
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tob = STAILQ_NEXT(to->to_lastblock, tob_list);
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if (tob == NULL)
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break;
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STAILQ_REMOVE_NEXT(&to->to_list, to->to_lastblock, tob_list);
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}
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uma_zfree(ttyoutq_zone, tob);
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to->to_nblocks--;
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}
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}
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size_t
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ttyoutq_read(struct ttyoutq *to, void *buf, size_t len)
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{
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char *cbuf = buf;
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while (len > 0) {
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struct ttyoutq_block *tob;
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size_t cbegin, cend, clen;
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/* See if there still is data. */
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if (to->to_begin == to->to_end)
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break;
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tob = STAILQ_FIRST(&to->to_list);
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if (tob == NULL)
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break;
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/*
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* The end address should be the lowest of these three:
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* - The write pointer
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* - The blocksize - we can't read beyond the block
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* - The end address if we could perform the full read
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*/
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cbegin = to->to_begin;
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cend = MIN(MIN(to->to_end, to->to_begin + len),
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TTYOUTQ_DATASIZE);
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clen = cend - cbegin;
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if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) {
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/* Read the block until the end. */
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STAILQ_REMOVE_HEAD(&to->to_list, tob_list);
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STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list);
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to->to_begin = 0;
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if (to->to_end <= TTYOUTQ_DATASIZE) {
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to->to_end = 0;
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} else {
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to->to_end -= TTYOUTQ_DATASIZE;
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}
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} else {
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/* Read the block partially. */
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to->to_begin += clen;
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}
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/* Copy the data out of the buffers. */
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memcpy(cbuf, tob->tob_data + cbegin, clen);
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cbuf += clen;
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len -= clen;
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}
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return (cbuf - (char *)buf);
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}
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/*
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* An optimized version of ttyoutq_read() which can be used in pseudo
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* TTY drivers to directly copy data from the outq to userspace, instead
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* of buffering it.
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*
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* We can only copy data directly if we need to read the entire block
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* back to the user, because we temporarily remove the block from the
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* queue. Otherwise we need to copy it to a temporary buffer first, to
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* make sure data remains in the correct order.
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*/
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int
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ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio)
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{
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while (uio->uio_resid > 0) {
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int error;
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struct ttyoutq_block *tob;
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size_t cbegin, cend, clen;
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/* See if there still is data. */
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if (to->to_begin == to->to_end)
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return (0);
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tob = STAILQ_FIRST(&to->to_list);
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if (tob == NULL)
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return (0);
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/*
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* The end address should be the lowest of these three:
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* - The write pointer
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* - The blocksize - we can't read beyond the block
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* - The end address if we could perform the full read
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*/
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cbegin = to->to_begin;
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cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid),
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TTYOUTQ_DATASIZE);
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clen = cend - cbegin;
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/*
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* We can prevent buffering in some cases:
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* - We need to read the block until the end.
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* - We don't need to read the block until the end, but
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* there is no data beyond it, which allows us to move
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* the write pointer to a new block.
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*/
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if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) {
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atomic_add_long(&ttyoutq_nfast, 1);
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/*
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* Fast path: zero copy. Remove the first block,
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* so we can unlock the TTY temporarily.
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*/
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STAILQ_REMOVE_HEAD(&to->to_list, tob_list);
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to->to_nblocks--;
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to->to_begin = 0;
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if (to->to_end <= TTYOUTQ_DATASIZE) {
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to->to_end = 0;
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} else {
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to->to_end -= TTYOUTQ_DATASIZE;
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}
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/* Temporary unlock and copy the data to userspace. */
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tty_unlock(tp);
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error = uiomove(tob->tob_data + cbegin, clen, uio);
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tty_lock(tp);
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/* Block can now be readded to the list. */
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/*
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* XXX: we could remove the blocks here when the
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* queue was shrunk, but still in use. See
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* ttyoutq_setsize().
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*/
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STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list);
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to->to_nblocks++;
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if (error != 0)
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return (error);
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} else {
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char ob[TTYOUTQ_DATASIZE - 1];
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atomic_add_long(&ttyoutq_nslow, 1);
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/*
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* Slow path: store data in a temporary buffer.
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*/
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memcpy(ob, tob->tob_data + cbegin, clen);
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to->to_begin += clen;
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MPASS(to->to_begin < TTYOUTQ_DATASIZE);
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/* Temporary unlock and copy the data to userspace. */
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tty_unlock(tp);
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error = uiomove(ob, clen, uio);
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tty_lock(tp);
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if (error != 0)
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return (error);
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}
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}
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return (0);
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}
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size_t
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ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes)
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{
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const char *cbuf = buf;
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struct ttyoutq_block *tob;
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unsigned int boff;
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size_t l;
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while (nbytes > 0) {
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/* Offset in current block. */
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tob = to->to_lastblock;
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boff = to->to_end % TTYOUTQ_DATASIZE;
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if (to->to_end == 0) {
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/* First time we're being used or drained. */
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MPASS(to->to_begin == 0);
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tob = to->to_lastblock = STAILQ_FIRST(&to->to_list);
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if (tob == NULL) {
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/* Queue has no blocks. */
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break;
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}
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} else if (boff == 0) {
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/* We reached the end of this block on last write. */
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tob = STAILQ_NEXT(tob, tob_list);
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if (tob == NULL) {
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/* We've reached the watermark. */
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break;
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}
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to->to_lastblock = tob;
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}
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/* Don't copy more than was requested. */
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l = MIN(nbytes, TTYOUTQ_DATASIZE - boff);
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MPASS(l > 0);
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memcpy(tob->tob_data + boff, cbuf, l);
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cbuf += l;
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nbytes -= l;
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to->to_end += l;
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}
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return (cbuf - (const char *)buf);
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}
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int
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ttyoutq_write_nofrag(struct ttyoutq *to, const void *buf, size_t nbytes)
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{
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size_t ret;
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if (ttyoutq_bytesleft(to) < nbytes)
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return (-1);
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/* We should always be able to write it back. */
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ret = ttyoutq_write(to, buf, nbytes);
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MPASS(ret == nbytes);
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return (0);
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}
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static void
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ttyoutq_startup(void *dummy)
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{
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ttyoutq_zone = uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block),
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NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
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}
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SYSINIT(ttyoutq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyoutq_startup, NULL);
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