X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/c0fea4742e91338fffdcf79f86a7c1d5e2b97eb1..8ad349bb6ed4a0be06e34c92be0d98b92e078db4:/iokit/Kernel/IORegistryEntry.cpp diff --git a/iokit/Kernel/IORegistryEntry.cpp b/iokit/Kernel/IORegistryEntry.cpp index 4be7e3aa5..5bc48d6e9 100644 --- a/iokit/Kernel/IORegistryEntry.cpp +++ b/iokit/Kernel/IORegistryEntry.cpp @@ -1,23 +1,31 @@ /* * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved. * - * @APPLE_LICENSE_HEADER_START@ + * @APPLE_LICENSE_OSREFERENCE_HEADER_START@ * - * The contents of this file constitute Original Code as defined in and - * are subject to the Apple Public Source License Version 1.1 (the - * "License"). You may not use this file except in compliance with the - * License. Please obtain a copy of the License at - * http://www.apple.com/publicsource and read it before using this file. - * - * This Original Code and all software distributed under the License are - * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER - * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, - * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, - * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the - * License for the specific language governing rights and limitations - * under the License. - * - * @APPLE_LICENSE_HEADER_END@ + * This file contains Original Code and/or Modifications of Original Code + * as defined in and that are subject to the Apple Public Source License + * Version 2.0 (the 'License'). You may not use this file except in + * compliance with the License. The rights granted to you under the + * License may not be used to create, or enable the creation or + * redistribution of, unlawful or unlicensed copies of an Apple operating + * system, or to circumvent, violate, or enable the circumvention or + * violation of, any terms of an Apple operating system software license + * agreement. + * + * Please obtain a copy of the License at + * http://www.opensource.apple.com/apsl/ and read it before using this + * file. + * + * The Original Code and all software distributed under the License are + * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER + * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, + * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. + * Please see the License for the specific language governing rights and + * limitations under the License. + * + * @APPLE_LICENSE_OSREFERENCE_HEADER_END@ */ /* * Copyright (c) 1998 Apple Computer, Inc. All rights reserved. @@ -87,9 +95,9 @@ OSDefineMetaClassAndStructors(IORegistryPlane, OSObject) static IORecursiveLock * gPropertiesLock; static SInt32 gIORegistryGenerationCount; -#define UNLOCK lck_rw_done( &gIORegistryLock ) -#define RLOCK lck_rw_lock_shared( &gIORegistryLock ) -#define WLOCK lck_rw_lock_exclusive( &gIORegistryLock ); \ +#define UNLOCK s_lock_done( &gIORegistryLock ) +#define RLOCK s_lock_read( &gIORegistryLock ) +#define WLOCK s_lock_write( &gIORegistryLock ); \ gIORegistryGenerationCount++ // make atomic @@ -108,11 +116,170 @@ static SInt32 gIORegistryGenerationCount; /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ -lck_rw_t gIORegistryLock; -lck_grp_t *gIORegistryLockGrp; -lck_grp_attr_t *gIORegistryLockGrpAttr; -lck_attr_t *gIORegistryLockAttr; +struct s_lock_t { + lck_spin_t interlock; /* "hardware" interlock field */ + volatile unsigned int + read_count:16, /* No. of accepted readers */ + want_upgrade:1, /* Read-to-write upgrade waiting */ + want_write:1, /* Writer is waiting, or + locked for write */ + waiting:1, /* Someone is sleeping on lock */ + can_sleep:1; /* Can attempts to lock go to sleep? */ +}; + +static struct s_lock_t gIORegistryLock; + +/* Time we loop without holding the interlock. + * The former is for when we cannot sleep, the latter + * for when our thread can go to sleep (loop less) + * we shouldn't retake the interlock at all frequently + * if we cannot go to sleep, since it interferes with + * any other processors. In particular, 100 is too small + * a number for powerpc MP systems because of cache + * coherency issues and differing lock fetch times between + * the processors + */ +static unsigned int lock_wait_time[2] = { (unsigned int)-1, 100 } ; + +static void +s_lock_init( + s_lock_t *l, + boolean_t can_sleep) +{ + (void) memset((void *) l, 0, sizeof(s_lock_t)); + + lck_spin_init(&l->interlock, IOLockGroup, LCK_ATTR_NULL); + l->want_write = FALSE; + l->want_upgrade = FALSE; + l->read_count = 0; + l->can_sleep = can_sleep; +} + +static void +s_lock_write( + register s_lock_t * l) +{ + register int i; + + lck_spin_lock(&l->interlock); + /* + * Try to acquire the want_write bit. + */ + while (l->want_write) { + + i = lock_wait_time[l->can_sleep ? 1 : 0]; + if (i != 0) { + lck_spin_unlock(&l->interlock); + while (--i != 0 && l->want_write) + continue; + lck_spin_lock(&l->interlock); + } + + if (l->can_sleep && l->want_write) { + l->waiting = TRUE; + lck_spin_sleep( &l->interlock, LCK_SLEEP_DEFAULT, + (event_t) l, THREAD_UNINT); + /* interlock relocked */ + } + } + l->want_write = TRUE; + + /* Wait for readers (and upgrades) to finish */ + + while ((l->read_count != 0) || l->want_upgrade) { + + i = lock_wait_time[l->can_sleep ? 1 : 0]; + if (i != 0) { + lck_spin_unlock(&l->interlock); + while (--i != 0 && (l->read_count != 0 || + l->want_upgrade)) + continue; + lck_spin_lock(&l->interlock); + } + + if (l->can_sleep && (l->read_count != 0 || l->want_upgrade)) { + l->waiting = TRUE; + lck_spin_sleep( &l->interlock, LCK_SLEEP_DEFAULT, + (event_t) l, THREAD_UNINT); + /* interlock relocked */ + } + } + + lck_spin_unlock(&l->interlock); +} + +static void +s_lock_done( + register s_lock_t * l) +{ + boolean_t do_wakeup = FALSE; + + lck_spin_lock(&l->interlock); + + if (l->read_count != 0) { + l->read_count -= 1; + } + else { + if (l->want_upgrade) { + l->want_upgrade = FALSE; + } + else { + l->want_write = FALSE; + } + } + + /* + * There is no reason to wakeup a waiting thread + * if the read-count is non-zero. Consider: + * we must be dropping a read lock + * threads are waiting only if one wants a write lock + * if there are still readers, they can't proceed + */ + if (l->waiting && (l->read_count == 0)) { + l->waiting = FALSE; + do_wakeup = TRUE; + } + + lck_spin_unlock(&l->interlock); + + if (do_wakeup) + thread_wakeup((event_t) l); +} + +static void +s_lock_read( + register s_lock_t * l) +{ + register int i; + + lck_spin_lock(&l->interlock); + + while ( l->want_upgrade || ((0 == l->read_count) && l->want_write )) { + + i = lock_wait_time[l->can_sleep ? 1 : 0]; + + if (i != 0) { + lck_spin_unlock(&l->interlock); + while (--i != 0 && + (l->want_upgrade || ((0 == l->read_count) && l->want_write ))) + continue; + lck_spin_lock(&l->interlock); + } + + if (l->can_sleep && + (l->want_upgrade || ((0 == l->read_count) && l->want_write ))) { + l->waiting = TRUE; + lck_spin_sleep( &l->interlock, LCK_SLEEP_DEFAULT, + (event_t) l, THREAD_UNINT); + /* interlock relocked */ + } + } + + l->read_count += 1; + lck_spin_unlock(&l->interlock); + +} /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ @@ -122,15 +289,7 @@ IORegistryEntry * IORegistryEntry::initialize( void ) if( !gRegistryRoot) { - - gIORegistryLockGrpAttr = lck_grp_attr_alloc_init(); - //lck_grp_attr_setstat(gIORegistryLockGrpAttr); - gIORegistryLockGrp = lck_grp_alloc_init("IORegistryLock", gIORegistryLockGrpAttr); - gIORegistryLockAttr = lck_attr_alloc_init(); - lck_attr_rw_shared_priority(gIORegistryLockAttr); - //lck_attr_setdebug(gIORegistryLockAttr); - lck_rw_init( &gIORegistryLock, gIORegistryLockGrp, gIORegistryLockAttr); - + s_lock_init( &gIORegistryLock, true ); gRegistryRoot = new IORegistryEntry; gPropertiesLock = IORecursiveLockAlloc(); gIORegistryPlanes = OSDictionary::withCapacity( 1 );