CC: kbuild-...@lists.01.org CC: linux-ker...@vger.kernel.org TO: Thomas Gleixner <t...@linutronix.de> CC: Ingo Molnar <mi...@kernel.org>
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 0c18f29aae7ce3dadd26d8ee3505d07cc982df75 commit: 70c80103aafdeae99126694bc1cd54de016bc258 locking/rtmutex: Consolidate the fast/slowpath invocation date: 3 months ago :::::: branch date: 11 hours ago :::::: commit date: 3 months ago config: powerpc64-randconfig-m031-20210622 (attached as .config) compiler: powerpc64le-linux-gcc (GCC) 9.3.0 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <l...@intel.com> Reported-by: Dan Carpenter <dan.carpen...@oracle.com> smatch warnings: kernel/locking/rtmutex.c:1375 rt_mutex_slowunlock() warn: inconsistent returns '&lock->wait_lock'. kernel/locking/rtmutex.c:1375 rt_mutex_slowunlock() warn: inconsistent returns 'flags'. vim +1375 kernel/locking/rtmutex.c 70c80103aafdea kernel/locking/rtmutex.c Thomas Gleixner 2021-03-26 1311 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1312 /* 802ab58da74bb4 kernel/locking/rtmutex.c Sebastian Andrzej Siewior 2015-06-17 1313 * Slow path to release a rt-mutex. aa2bfe55366552 kernel/locking/rtmutex.c Peter Zijlstra 2017-03-23 1314 * aa2bfe55366552 kernel/locking/rtmutex.c Peter Zijlstra 2017-03-23 1315 * Return whether the current task needs to call rt_mutex_postunlock(). 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1316 */ 70c80103aafdea kernel/locking/rtmutex.c Thomas Gleixner 2021-03-26 1317 static void __sched rt_mutex_slowunlock(struct rt_mutex *lock) 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1318 { 70c80103aafdea kernel/locking/rtmutex.c Thomas Gleixner 2021-03-26 1319 DEFINE_WAKE_Q(wake_q); b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1320 unsigned long flags; b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1321 b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1322 /* irqsave required to support early boot calls */ b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1323 raw_spin_lock_irqsave(&lock->wait_lock, flags); 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1324 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1325 debug_rt_mutex_unlock(lock); 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1326 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1327 /* 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1328 * We must be careful here if the fast path is enabled. If we 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1329 * have no waiters queued we cannot set owner to NULL here 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1330 * because of: 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1331 * 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1332 * foo->lock->owner = NULL; 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1333 * rtmutex_lock(foo->lock); <- fast path 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1334 * free = atomic_dec_and_test(foo->refcnt); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1335 * rtmutex_unlock(foo->lock); <- fast path 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1336 * if (free) 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1337 * kfree(foo); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1338 * raw_spin_unlock(foo->lock->wait_lock); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1339 * 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1340 * So for the fastpath enabled kernel: 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1341 * 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1342 * Nothing can set the waiters bit as long as we hold 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1343 * lock->wait_lock. So we do the following sequence: 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1344 * 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1345 * owner = rt_mutex_owner(lock); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1346 * clear_rt_mutex_waiters(lock); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1347 * raw_spin_unlock(&lock->wait_lock); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1348 * if (cmpxchg(&lock->owner, owner, 0) == owner) 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1349 * return; 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1350 * goto retry; 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1351 * 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1352 * The fastpath disabled variant is simple as all access to 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1353 * lock->owner is serialized by lock->wait_lock: 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1354 * 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1355 * lock->owner = NULL; 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1356 * raw_spin_unlock(&lock->wait_lock); 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1357 */ 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1358 while (!rt_mutex_has_waiters(lock)) { 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1359 /* Drops lock->wait_lock ! */ b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1360 if (unlock_rt_mutex_safe(lock, flags) == true) 70c80103aafdea kernel/locking/rtmutex.c Thomas Gleixner 2021-03-26 1361 return; 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1362 /* Relock the rtmutex and try again */ b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1363 raw_spin_lock_irqsave(&lock->wait_lock, flags); 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1364 } 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1365 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1366 /* 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1367 * The wakeup next waiter path does not suffer from the above 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1368 * race. See the comments there. 45ab4effc3bee6 kernel/locking/rtmutex.c Davidlohr Bueso 2015-05-19 1369 * 45ab4effc3bee6 kernel/locking/rtmutex.c Davidlohr Bueso 2015-05-19 1370 * Queue the next waiter for wakeup once we release the wait_lock. 27e35715df54cb kernel/locking/rtmutex.c Thomas Gleixner 2014-06-11 1371 */ 70c80103aafdea kernel/locking/rtmutex.c Thomas Gleixner 2021-03-26 1372 mark_wakeup_next_waiter(&wake_q, lock); b4abf91047cf05 kernel/locking/rtmutex.c Thomas Gleixner 2016-01-13 1373 raw_spin_unlock_irqrestore(&lock->wait_lock, flags); 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1374 70c80103aafdea kernel/locking/rtmutex.c Thomas Gleixner 2021-03-26 @1375 rt_mutex_postunlock(&wake_q); 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1376 } 23f78d4a03c53c kernel/rtmutex.c Ingo Molnar 2006-06-27 1377 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-...@lists.01.org
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