Re: [PATCH printk v1 06/18] printk: nobkl: Add acquire/release logic
From: Dan Carpenter
Date: Mon Mar 06 2023 - 04:08:05 EST
Hi John,
url: https://github.com/intel-lab-lkp/linux/commits/John-Ogness/kdb-do-not-assume-write-callback-available/20230303-040039
base: 10d639febe5629687dac17c4a7500a96537ce11a
patch link: https://lore.kernel.org/r/20230302195618.156940-7-john.ogness%40linutronix.de
patch subject: [PATCH printk v1 06/18] printk: nobkl: Add acquire/release logic
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20230305/202303051319.m55kZE3v-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <error27@xxxxxxxxx>
| Link: https://lore.kernel.org/r/202303051319.m55kZE3v-lkp@xxxxxxxxx/
smatch warnings:
kernel/printk/printk_nobkl.c:391 cons_try_acquire_spin() warn: signedness bug returning '(-16)'
vim +391 kernel/printk/printk_nobkl.c
d444c8549ebdf3 Thomas Gleixner 2023-03-02 284 /**
d444c8549ebdf3 Thomas Gleixner 2023-03-02 285 * cons_try_acquire_spin - Complete the spinwait attempt
d444c8549ebdf3 Thomas Gleixner 2023-03-02 286 * @ctxt: Pointer to an acquire context that contains
d444c8549ebdf3 Thomas Gleixner 2023-03-02 287 * all information about the acquire mode
d444c8549ebdf3 Thomas Gleixner 2023-03-02 288 *
d444c8549ebdf3 Thomas Gleixner 2023-03-02 289 * @ctxt->hov_state contains the handover state that was set in
d444c8549ebdf3 Thomas Gleixner 2023-03-02 290 * state[REQ]
d444c8549ebdf3 Thomas Gleixner 2023-03-02 291 * @ctxt->req_state contains the request state that was set in
d444c8549ebdf3 Thomas Gleixner 2023-03-02 292 * state[CUR]
d444c8549ebdf3 Thomas Gleixner 2023-03-02 293 *
d444c8549ebdf3 Thomas Gleixner 2023-03-02 294 * Returns: 0 if successfully locked. -EBUSY on timeout. -EAGAIN on
d444c8549ebdf3 Thomas Gleixner 2023-03-02 295 * unexpected state values.
Out of date comments.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 296 *
d444c8549ebdf3 Thomas Gleixner 2023-03-02 297 * On success @ctxt->state contains the new state that was set in
d444c8549ebdf3 Thomas Gleixner 2023-03-02 298 * state[CUR]
d444c8549ebdf3 Thomas Gleixner 2023-03-02 299 *
d444c8549ebdf3 Thomas Gleixner 2023-03-02 300 * On -EBUSY failure this context timed out. This context should either
d444c8549ebdf3 Thomas Gleixner 2023-03-02 301 * give up or attempt a hostile takeover.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 302 *
d444c8549ebdf3 Thomas Gleixner 2023-03-02 303 * On -EAGAIN failure this context encountered unexpected state values.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 304 * This context should retry the full handover request setup process (the
d444c8549ebdf3 Thomas Gleixner 2023-03-02 305 * handover request setup by cons_setup_handover() is now invalidated and
d444c8549ebdf3 Thomas Gleixner 2023-03-02 306 * must be performed again).
Out of date.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 307 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 308 static bool cons_try_acquire_spin(struct cons_context *ctxt)
^^^^
After reviewing the code, it looks the intention was the bool should be
changed to int.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 309 {
d444c8549ebdf3 Thomas Gleixner 2023-03-02 310 struct console *con = ctxt->console;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 311 struct cons_state cur;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 312 struct cons_state new;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 313 int err = -EAGAIN;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 314 int timeout;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 315
d444c8549ebdf3 Thomas Gleixner 2023-03-02 316 /* Now wait for the other side to hand over */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 317 for (timeout = ctxt->spinwait_max_us; timeout >= 0; timeout--) {
d444c8549ebdf3 Thomas Gleixner 2023-03-02 318 /* Timeout immediately if a remote panic is detected. */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 319 if (cons_check_panic())
d444c8549ebdf3 Thomas Gleixner 2023-03-02 320 break;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 321
d444c8549ebdf3 Thomas Gleixner 2023-03-02 322 cons_state_read(con, CON_STATE_CUR, &cur);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 323
d444c8549ebdf3 Thomas Gleixner 2023-03-02 324 /*
d444c8549ebdf3 Thomas Gleixner 2023-03-02 325 * If the real state of the console matches the handover state
d444c8549ebdf3 Thomas Gleixner 2023-03-02 326 * that this context setup, then the handover was a success
d444c8549ebdf3 Thomas Gleixner 2023-03-02 327 * and this context is now the owner.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 328 *
d444c8549ebdf3 Thomas Gleixner 2023-03-02 329 * Note that this might have raced with a new higher priority
d444c8549ebdf3 Thomas Gleixner 2023-03-02 330 * requester coming in after the lock was handed over.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 331 * However, that requester will see that the owner changes and
d444c8549ebdf3 Thomas Gleixner 2023-03-02 332 * setup a new request for the current owner (this context).
d444c8549ebdf3 Thomas Gleixner 2023-03-02 333 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 334 if (cons_state_bits_match(cur, ctxt->hov_state))
d444c8549ebdf3 Thomas Gleixner 2023-03-02 335 goto success;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 336
d444c8549ebdf3 Thomas Gleixner 2023-03-02 337 /*
d444c8549ebdf3 Thomas Gleixner 2023-03-02 338 * If state changed since the request was made, give up as
d444c8549ebdf3 Thomas Gleixner 2023-03-02 339 * it is no longer consistent. This must include
d444c8549ebdf3 Thomas Gleixner 2023-03-02 340 * state::req_prio since there could be a higher priority
d444c8549ebdf3 Thomas Gleixner 2023-03-02 341 * request available.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 342 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 343 if (cur.bits != ctxt->req_state.bits)
d444c8549ebdf3 Thomas Gleixner 2023-03-02 344 goto cleanup;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 345
d444c8549ebdf3 Thomas Gleixner 2023-03-02 346 /*
d444c8549ebdf3 Thomas Gleixner 2023-03-02 347 * Finally check whether the handover state is still
d444c8549ebdf3 Thomas Gleixner 2023-03-02 348 * the same.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 349 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 350 cons_state_read(con, CON_STATE_REQ, &cur);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 351 if (cur.atom != ctxt->hov_state.atom)
d444c8549ebdf3 Thomas Gleixner 2023-03-02 352 goto cleanup;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 353
d444c8549ebdf3 Thomas Gleixner 2023-03-02 354 /* Account time */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 355 if (timeout > 0)
d444c8549ebdf3 Thomas Gleixner 2023-03-02 356 udelay(1);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 357 }
d444c8549ebdf3 Thomas Gleixner 2023-03-02 358
d444c8549ebdf3 Thomas Gleixner 2023-03-02 359 /*
d444c8549ebdf3 Thomas Gleixner 2023-03-02 360 * Timeout. Cleanup the handover state and carefully try to reset
d444c8549ebdf3 Thomas Gleixner 2023-03-02 361 * req_prio in the real state. The reset is important to ensure
d444c8549ebdf3 Thomas Gleixner 2023-03-02 362 * that the owner does not hand over the lock after this context
d444c8549ebdf3 Thomas Gleixner 2023-03-02 363 * has given up waiting.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 364 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 365 cons_cleanup_handover(ctxt);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 366
d444c8549ebdf3 Thomas Gleixner 2023-03-02 367 cons_state_read(con, CON_STATE_CUR, &cur);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 368 do {
d444c8549ebdf3 Thomas Gleixner 2023-03-02 369 /*
d444c8549ebdf3 Thomas Gleixner 2023-03-02 370 * The timeout might have raced with the owner coming late
d444c8549ebdf3 Thomas Gleixner 2023-03-02 371 * and handing it over gracefully.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 372 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 373 if (cons_state_bits_match(cur, ctxt->hov_state))
d444c8549ebdf3 Thomas Gleixner 2023-03-02 374 goto success;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 375
d444c8549ebdf3 Thomas Gleixner 2023-03-02 376 /*
d444c8549ebdf3 Thomas Gleixner 2023-03-02 377 * Validate that the state matches with the state at request
d444c8549ebdf3 Thomas Gleixner 2023-03-02 378 * time. If this check fails, there is already a higher
d444c8549ebdf3 Thomas Gleixner 2023-03-02 379 * priority context waiting or the owner has changed (either
d444c8549ebdf3 Thomas Gleixner 2023-03-02 380 * by higher priority or by hostile takeover). In all fail
d444c8549ebdf3 Thomas Gleixner 2023-03-02 381 * cases this context is no longer in line for a handover to
d444c8549ebdf3 Thomas Gleixner 2023-03-02 382 * take place, so no reset is necessary.
d444c8549ebdf3 Thomas Gleixner 2023-03-02 383 */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 384 if (cur.bits != ctxt->req_state.bits)
d444c8549ebdf3 Thomas Gleixner 2023-03-02 385 goto cleanup;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 386
d444c8549ebdf3 Thomas Gleixner 2023-03-02 387 copy_full_state(new, cur);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 388 new.req_prio = 0;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 389 } while (!cons_state_try_cmpxchg(con, CON_STATE_CUR, &cur, &new));
d444c8549ebdf3 Thomas Gleixner 2023-03-02 390 /* Reset worked. Report timeout. */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 @391 return -EBUSY;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 392
d444c8549ebdf3 Thomas Gleixner 2023-03-02 393 success:
d444c8549ebdf3 Thomas Gleixner 2023-03-02 394 /* Store the real state */
d444c8549ebdf3 Thomas Gleixner 2023-03-02 395 copy_full_state(ctxt->state, cur);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 396 ctxt->hostile = false;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 397 err = 0;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 398
d444c8549ebdf3 Thomas Gleixner 2023-03-02 399 cleanup:
d444c8549ebdf3 Thomas Gleixner 2023-03-02 400 cons_cleanup_handover(ctxt);
d444c8549ebdf3 Thomas Gleixner 2023-03-02 401 return err;
d444c8549ebdf3 Thomas Gleixner 2023-03-02 402 }
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests