tty_outq.c revision 182471
1265879Sdes/*- 2265879Sdes * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org> 3265879Sdes * All rights reserved. 4265879Sdes * 543092Smarkm * Portions of this software were developed under sponsorship from Snow 651462Smarkm * B.V., the Netherlands. 751462Smarkm * 851462Smarkm * Redistribution and use in source and binary forms, with or without 951462Smarkm * modification, are permitted provided that the following conditions 1051462Smarkm * are met: 1151462Smarkm * 1. Redistributions of source code must retain the above copyright 1251462Smarkm * notice, this list of conditions and the following disclaimer. 1351462Smarkm * 2. Redistributions in binary form must reproduce the above copyright 1451462Smarkm * notice, this list of conditions and the following disclaimer in the 1551462Smarkm * documentation and/or other materials provided with the distribution. 1651462Smarkm * 1751462Smarkm * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 1851462Smarkm * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 1951462Smarkm * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 2051462Smarkm * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 2151462Smarkm * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 2251462Smarkm * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 2351462Smarkm * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 2451462Smarkm * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 2551462Smarkm * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 2642981Sbrandon * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 2742981Sbrandon * SUCH DAMAGE. 2883551Sdillon */ 2983551Sdillon 3042981Sbrandon#include <sys/cdefs.h> 3170419Speter__FBSDID("$FreeBSD: head/sys/kern/tty_outq.c 182471 2008-08-30 09:18:27Z ed $"); 32265879Sdes 33265879Sdes#include <sys/param.h> 3417141Sjkh#include <sys/kernel.h> 3591754Smarkm#include <sys/lock.h> 36265879Sdes#include <sys/queue.h> 3751462Smarkm#include <sys/sysctl.h> 381984Scsgr#include <sys/systm.h> 39265879Sdes#include <sys/tty.h> 40273043Sdes#include <sys/uio.h> 41273043Sdes 42273043Sdes#include <vm/uma.h> 43273043Sdes 44273043Sdes/* 45273043Sdes * TTY output queue buffering. 46273043Sdes * 47265879Sdes * The previous design of the TTY layer offered the so-called clists. 48265879Sdes * These clists were used for both the input queues and the output 4964918Sgreen * queue. We don't use certain features on the output side, like quoting 5064918Sgreen * bits for parity marking and such. This mechanism is similar to the 5164918Sgreen * old clists, but only contains the features we need to buffer the 52265879Sdes * output. 53265879Sdes */ 5474106Smarkm 55265879Sdes/* Statistics. */ 5674106Smarkmstatic long ttyoutq_nfast = 0; 57265879SdesSYSCTL_LONG(_kern, OID_AUTO, tty_outq_nfast, CTLFLAG_RD, 58265879Sdes &ttyoutq_nfast, 0, "Unbuffered reads to userspace on output"); 59273043Sdesstatic long ttyoutq_nslow = 0; 60236967SdesSYSCTL_LONG(_kern, OID_AUTO, tty_outq_nslow, CTLFLAG_RD, 61265879Sdes &ttyoutq_nslow, 0, "Buffered reads to userspace on output"); 62236967Sdes 63236967Sdesstruct ttyoutq_block { 64265879Sdes STAILQ_ENTRY(ttyoutq_block) tob_list; 65265879Sdes char tob_data[TTYOUTQ_DATASIZE]; 66265879Sdes}; 6764918Sgreen 68273043Sdesstatic uma_zone_t ttyoutq_zone; 69273043Sdes 7070419Spetervoid 71265879Sdesttyoutq_flush(struct ttyoutq *to) 72265879Sdes{ 7370419Speter 74265879Sdes to->to_begin = 0; 75265879Sdes to->to_end = 0; 76265879Sdes} 7764918Sgreen 7870419Spetervoid 7970419Speterttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size) 8064918Sgreen{ 81265879Sdes struct ttyoutq_block *tob; 8264918Sgreen 8364918Sgreen to->to_quota = howmany(size, TTYOUTQ_DATASIZE); 84265879Sdes 85265879Sdes while (to->to_quota > to->to_nblocks) { 86265879Sdes /* 8764918Sgreen * List is getting bigger. 88265879Sdes * Add new blocks to the tail of the list. 8970419Speter * 90265879Sdes * We must unlock the TTY temporarily, because we need 9164918Sgreen * to allocate memory. This won't be a problem, because 92265879Sdes * in the worst case, another thread ends up here, which 93265879Sdes * may cause us to allocate too many blocks, but this 94265879Sdes * will be caught by the loop below. 9564918Sgreen */ 9664918Sgreen tty_unlock(tp); 9764918Sgreen tob = uma_zalloc(ttyoutq_zone, M_WAITOK); 9864918Sgreen tty_lock(tp); 9964918Sgreen 10064918Sgreen STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list); 101265879Sdes to->to_nblocks++; 102265879Sdes } 103265879Sdes} 104265879Sdes 105265879Sdesvoid 10643092Smarkmttyoutq_free(struct ttyoutq *to) 10791754Smarkm{ 1081984Scsgr struct ttyoutq_block *tob; 109265879Sdes 110267111Sume ttyoutq_flush(to); 111267111Sume to->to_quota = 0; 112267111Sume 11364918Sgreen while ((tob = STAILQ_FIRST(&to->to_list)) != NULL) { 114265879Sdes STAILQ_REMOVE_HEAD(&to->to_list, tob_list); 115265879Sdes uma_zfree(ttyoutq_zone, tob); 116265879Sdes to->to_nblocks--; 117265879Sdes } 118267111Sume 119267111Sume MPASS(to->to_nblocks == 0); 120265879Sdes} 121265879Sdes 122265879Sdessize_t 1231984Scsgrttyoutq_read(struct ttyoutq *to, void *buf, size_t len) 124{ 125 char *cbuf = buf; 126 127 while (len > 0) { 128 struct ttyoutq_block *tob; 129 size_t cbegin, cend, clen; 130 131 /* See if there still is data. */ 132 if (to->to_begin == to->to_end) 133 break; 134 tob = STAILQ_FIRST(&to->to_list); 135 if (tob == NULL) 136 break; 137 138 /* 139 * The end address should be the lowest of these three: 140 * - The write pointer 141 * - The blocksize - we can't read beyond the block 142 * - The end address if we could perform the full read 143 */ 144 cbegin = to->to_begin; 145 cend = MIN(MIN(to->to_end, to->to_begin + len), 146 TTYOUTQ_DATASIZE); 147 clen = cend - cbegin; 148 149 if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) { 150 /* Read the block until the end. */ 151 STAILQ_REMOVE_HEAD(&to->to_list, tob_list); 152 if (to->to_quota < to->to_nblocks) { 153 uma_zfree(ttyoutq_zone, tob); 154 to->to_nblocks--; 155 } else { 156 STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list); 157 } 158 to->to_begin = 0; 159 if (to->to_end <= TTYOUTQ_DATASIZE) { 160 to->to_end = 0; 161 } else { 162 to->to_end -= TTYOUTQ_DATASIZE; 163 } 164 } else { 165 /* Read the block partially. */ 166 to->to_begin += clen; 167 } 168 169 /* Copy the data out of the buffers. */ 170 memcpy(cbuf, tob->tob_data + cbegin, clen); 171 cbuf += clen; 172 len -= clen; 173 } 174 175 return (cbuf - (char *)buf); 176} 177 178/* 179 * An optimized version of ttyoutq_read() which can be used in pseudo 180 * TTY drivers to directly copy data from the outq to userspace, instead 181 * of buffering it. 182 * 183 * We can only copy data directly if we need to read the entire block 184 * back to the user, because we temporarily remove the block from the 185 * queue. Otherwise we need to copy it to a temporary buffer first, to 186 * make sure data remains in the correct order. 187 */ 188int 189ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio) 190{ 191 192 while (uio->uio_resid > 0) { 193 int error; 194 struct ttyoutq_block *tob; 195 size_t cbegin, cend, clen; 196 197 /* See if there still is data. */ 198 if (to->to_begin == to->to_end) 199 return (0); 200 tob = STAILQ_FIRST(&to->to_list); 201 if (tob == NULL) 202 return (0); 203 204 /* 205 * The end address should be the lowest of these three: 206 * - The write pointer 207 * - The blocksize - we can't read beyond the block 208 * - The end address if we could perform the full read 209 */ 210 cbegin = to->to_begin; 211 cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid), 212 TTYOUTQ_DATASIZE); 213 clen = cend - cbegin; 214 215 /* 216 * We can prevent buffering in some cases: 217 * - We need to read the block until the end. 218 * - We don't need to read the block until the end, but 219 * there is no data beyond it, which allows us to move 220 * the write pointer to a new block. 221 */ 222 if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) { 223 atomic_add_long(&ttyoutq_nfast, 1); 224 225 /* 226 * Fast path: zero copy. Remove the first block, 227 * so we can unlock the TTY temporarily. 228 */ 229 STAILQ_REMOVE_HEAD(&to->to_list, tob_list); 230 to->to_nblocks--; 231 to->to_begin = 0; 232 if (to->to_end <= TTYOUTQ_DATASIZE) { 233 to->to_end = 0; 234 } else { 235 to->to_end -= TTYOUTQ_DATASIZE; 236 } 237 238 /* Temporary unlock and copy the data to userspace. */ 239 tty_unlock(tp); 240 error = uiomove(tob->tob_data + cbegin, clen, uio); 241 tty_lock(tp); 242 243 /* Block can now be readded to the list. */ 244 if (to->to_quota <= to->to_nblocks) { 245 uma_zfree(ttyoutq_zone, tob); 246 } else { 247 STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list); 248 to->to_nblocks++; 249 } 250 } else { 251 char ob[TTYOUTQ_DATASIZE - 1]; 252 atomic_add_long(&ttyoutq_nslow, 1); 253 254 /* 255 * Slow path: store data in a temporary buffer. 256 */ 257 memcpy(ob, tob->tob_data + cbegin, clen); 258 to->to_begin += clen; 259 MPASS(to->to_begin < TTYOUTQ_DATASIZE); 260 261 /* Temporary unlock and copy the data to userspace. */ 262 tty_unlock(tp); 263 error = uiomove(ob, clen, uio); 264 tty_lock(tp); 265 } 266 267 if (error != 0) 268 return (error); 269 } 270 271 return (0); 272} 273 274size_t 275ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes) 276{ 277 const char *cbuf = buf; 278 struct ttyoutq_block *tob; 279 unsigned int boff; 280 size_t l; 281 282 while (nbytes > 0) { 283 /* Offset in current block. */ 284 tob = to->to_lastblock; 285 boff = to->to_end % TTYOUTQ_DATASIZE; 286 287 if (to->to_end == 0) { 288 /* First time we're being used or drained. */ 289 MPASS(to->to_begin == 0); 290 tob = to->to_lastblock = STAILQ_FIRST(&to->to_list); 291 if (tob == NULL) { 292 /* Queue has no blocks. */ 293 break; 294 } 295 } else if (boff == 0) { 296 /* We reached the end of this block on last write. */ 297 tob = STAILQ_NEXT(tob, tob_list); 298 if (tob == NULL) { 299 /* We've reached the watermark. */ 300 break; 301 } 302 to->to_lastblock = tob; 303 } 304 305 /* Don't copy more than was requested. */ 306 l = MIN(nbytes, TTYOUTQ_DATASIZE - boff); 307 MPASS(l > 0); 308 memcpy(tob->tob_data + boff, cbuf, l); 309 310 cbuf += l; 311 nbytes -= l; 312 to->to_end += l; 313 } 314 315 return (cbuf - (const char *)buf); 316} 317 318int 319ttyoutq_write_nofrag(struct ttyoutq *to, const void *buf, size_t nbytes) 320{ 321 size_t ret; 322 323 if (ttyoutq_bytesleft(to) < nbytes) 324 return (-1); 325 326 /* We should always be able to write it back. */ 327 ret = ttyoutq_write(to, buf, nbytes); 328 MPASS(ret == nbytes); 329 330 return (0); 331} 332 333static void 334ttyoutq_startup(void *dummy) 335{ 336 337 ttyoutq_zone = uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block), 338 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 339} 340 341SYSINIT(ttyoutq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyoutq_startup, NULL); 342