int owner_rw(const struct lock_object *lock, struct thread **owner) { const struct rwlock *rw = (const struct rwlock *)lock; uintptr_t x = rw->rw_lock; *owner = rw_wowner(rw); return ((x & RW_LOCK_READ) != 0 ? (RW_READERS(x) != 0) : (*owner != NULL)); }
void db_show_rwlock(const struct lock_object *lock) { const struct rwlock *rw; struct thread *td; rw = (const struct rwlock *)lock; db_printf(" state: "); if (rw->rw_lock == RW_UNLOCKED) db_printf("UNLOCKED\n"); else if (rw->rw_lock == RW_DESTROYED) { db_printf("DESTROYED\n"); return; } else if (rw->rw_lock & RW_LOCK_READ) db_printf("RLOCK: %ju locks\n", (uintmax_t)(RW_READERS(rw->rw_lock))); else { td = rw_wowner(rw); db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_name); if (rw_recursed(rw)) db_printf(" recursed: %u\n", rw->rw_recurse); } db_printf(" waiters: "); switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { case RW_LOCK_READ_WAITERS: db_printf("readers\n"); break; case RW_LOCK_WRITE_WAITERS: db_printf("writers\n"); break; case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: db_printf("readers and writers\n"); break; default: db_printf("none\n"); break; } }
void __rw_rlock(volatile uintptr_t *c, const char *file, int line) { struct rwlock *rw; struct turnstile *ts; #ifdef ADAPTIVE_RWLOCKS volatile struct thread *owner; int spintries = 0; int i; #endif #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif uintptr_t v; #ifdef KDTRACE_HOOKS uintptr_t state; uint64_t spin_cnt = 0; uint64_t sleep_cnt = 0; int64_t sleep_time = 0; int64_t all_time = 0; #endif if (SCHEDULER_STOPPED()) return; rw = rwlock2rw(c); KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread), ("rw_rlock() by idle thread %p on rwlock %s @ %s:%d", curthread, rw->lock_object.lo_name, file, line)); KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); KASSERT(rw_wowner(rw) != curthread, ("rw_rlock: wlock already held for %s @ %s:%d", rw->lock_object.lo_name, file, line)); WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL); #ifdef KDTRACE_HOOKS all_time -= lockstat_nsecs(&rw->lock_object); state = rw->rw_lock; #endif for (;;) { /* * Handle the easy case. If no other thread has a write * lock, then try to bump up the count of read locks. Note * that we have to preserve the current state of the * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a * read lock, then rw_lock must have changed, so restart * the loop. Note that this handles the case of a * completely unlocked rwlock since such a lock is encoded * as a read lock with no waiters. */ v = rw->rw_lock; if (RW_CAN_READ(v)) { /* * The RW_LOCK_READ_WAITERS flag should only be set * if the lock has been unlocked and write waiters * were present. */ if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, v + RW_ONE_READER)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", __func__, rw, (void *)v, (void *)(v + RW_ONE_READER)); break; } continue; } #ifdef KDTRACE_HOOKS spin_cnt++; #endif #ifdef HWPMC_HOOKS PMC_SOFT_CALL( , , lock, failed); #endif lock_profile_obtain_lock_failed(&rw->lock_object, &contested, &waittime); #ifdef ADAPTIVE_RWLOCKS /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock * changes. */ if ((v & RW_LOCK_READ) == 0) { owner = (struct thread *)RW_OWNER(v); if (TD_IS_RUNNING(owner)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, rw, owner); KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), "spinning", "lockname:\"%s\"", rw->lock_object.lo_name); while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && TD_IS_RUNNING(owner)) { cpu_spinwait(); #ifdef KDTRACE_HOOKS spin_cnt++; #endif } KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), "running"); continue; } } else if (spintries < rowner_retries) { spintries++; KTR_STATE1(KTR_SCHED, "thread", sched_tdname(curthread), "spinning", "lockname:\"%s\"", rw->lock_object.lo_name); for (i = 0; i < rowner_loops; i++) { v = rw->rw_lock; if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v)) break; cpu_spinwait(); } #ifdef KDTRACE_HOOKS spin_cnt += rowner_loops - i; #endif KTR_STATE0(KTR_SCHED, "thread", sched_tdname(curthread), "running"); if (i != rowner_loops) continue; } #endif /* * Okay, now it's the hard case. Some other thread already * has a write lock or there are write waiters present, * acquire the turnstile lock so we can begin the process * of blocking. */ ts = turnstile_trywait(&rw->lock_object); /* * The lock might have been released while we spun, so * recheck its state and restart the loop if needed. */ v = rw->rw_lock; if (RW_CAN_READ(v)) { turnstile_cancel(ts); continue; } #ifdef ADAPTIVE_RWLOCKS /* * The current lock owner might have started executing * on another CPU (or the lock could have changed * owners) while we were waiting on the turnstile * chain lock. If so, drop the turnstile lock and try * again. */ if ((v & RW_LOCK_READ) == 0) { owner = (struct thread *)RW_OWNER(v); if (TD_IS_RUNNING(owner)) { turnstile_cancel(ts); continue; } } #endif /* * The lock is held in write mode or it already has waiters. */ MPASS(!RW_CAN_READ(v)); /* * If the RW_LOCK_READ_WAITERS flag is already set, then * we can go ahead and block. If it is not set then try * to set it. If we fail to set it drop the turnstile * lock and restart the loop. */ if (!(v & RW_LOCK_READ_WAITERS)) { if (!atomic_cmpset_ptr(&rw->rw_lock, v, v | RW_LOCK_READ_WAITERS)) { turnstile_cancel(ts); continue; } if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p set read waiters flag", __func__, rw); } /* * We were unable to acquire the lock and the read waiters * flag is set, so we must block on the turnstile. */ if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, rw); #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(&rw->lock_object); #endif turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(&rw->lock_object); sleep_cnt++; #endif if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p resuming from turnstile", __func__, rw); } #ifdef KDTRACE_HOOKS all_time += lockstat_nsecs(&rw->lock_object); if (sleep_time) LOCKSTAT_RECORD4(rw__block, rw, sleep_time, LOCKSTAT_READER, (state & RW_LOCK_READ) == 0, (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state)); /* Record only the loops spinning and not sleeping. */ if (spin_cnt > sleep_cnt) LOCKSTAT_RECORD4(rw__spin, rw, all_time - sleep_time, LOCKSTAT_READER, (state & RW_LOCK_READ) == 0, (state & RW_LOCK_READ) == 0 ? 0 : RW_READERS(state)); #endif /* * TODO: acquire "owner of record" here. Here be turnstile dragons * however. turnstiles don't like owners changing between calls to * turnstile_wait() currently. */ LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(rw__acquire, rw, contested, waittime, file, line, LOCKSTAT_READER); LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); WITNESS_LOCK(&rw->lock_object, 0, file, line); curthread->td_locks++; curthread->td_rw_rlocks++; }
int _rw_wowned(const volatile uintptr_t *c) { return (rw_wowner(rwlock2rw(c)) == curthread); }
/* * In the non-WITNESS case, rw_assert() can only detect that at least * *some* thread owns an rlock, but it cannot guarantee that *this* * thread owns an rlock. */ void __rw_assert(const volatile uintptr_t *c, int what, const char *file, int line) { const struct rwlock *rw; if (panicstr != NULL) return; rw = rwlock2rw(c); switch (what) { case RA_LOCKED: case RA_LOCKED | RA_RECURSED: case RA_LOCKED | RA_NOTRECURSED: case RA_RLOCKED: case RA_RLOCKED | RA_RECURSED: case RA_RLOCKED | RA_NOTRECURSED: #ifdef WITNESS witness_assert(&rw->lock_object, what, file, line); #else /* * If some other thread has a write lock or we have one * and are asserting a read lock, fail. Also, if no one * has a lock at all, fail. */ if (rw->rw_lock == RW_UNLOCKED || (!(rw->rw_lock & RW_LOCK_READ) && (what & RA_RLOCKED || rw_wowner(rw) != curthread))) panic("Lock %s not %slocked @ %s:%d\n", rw->lock_object.lo_name, (what & RA_RLOCKED) ? "read " : "", file, line); if (!(rw->rw_lock & RW_LOCK_READ) && !(what & RA_RLOCKED)) { if (rw_recursed(rw)) { if (what & RA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); } else if (what & RA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); } #endif break; case RA_WLOCKED: case RA_WLOCKED | RA_RECURSED: case RA_WLOCKED | RA_NOTRECURSED: if (rw_wowner(rw) != curthread) panic("Lock %s not exclusively locked @ %s:%d\n", rw->lock_object.lo_name, file, line); if (rw_recursed(rw)) { if (what & RA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); } else if (what & RA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); break; case RA_UNLOCKED: #ifdef WITNESS witness_assert(&rw->lock_object, what, file, line); #else /* * If we hold a write lock fail. We can't reliably check * to see if we hold a read lock or not. */ if (rw_wowner(rw) == curthread) panic("Lock %s exclusively locked @ %s:%d\n", rw->lock_object.lo_name, file, line); #endif break; default: panic("Unknown rw lock assertion: %d @ %s:%d", what, file, line); } }
int rw_wowned(const struct rwlock *rw) { return (rw_wowner(rw) == curthread); }