Date: Mon, 17 Aug 2009 16:17:21 +0000 (UTC) From: Attilio Rao <attilio@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r196334 - in head/sys: kern sys Message-ID: <200908171617.n7HGHLJs083432@svn.freebsd.org>
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Author: attilio Date: Mon Aug 17 16:17:21 2009 New Revision: 196334 URL: http://svn.freebsd.org/changeset/base/196334 Log: * Change the scope of the ASSERT_ATOMIC_LOAD() from a generic check to a pointer-fetching specific operation check. Consequently, rename the operation ASSERT_ATOMIC_LOAD_PTR(). * Fix the implementation of ASSERT_ATOMIC_LOAD_PTR() by checking directly alignment on the word boundry, for all the given specific architectures. That's a bit too strict for some common case, but it assures safety. * Add a comment explaining the scope of the macro * Add a new stub in the lockmgr specific implementation Tested by: marcel (initial version), marius Reviewed by: rwatson, jhb (comment specific review) Approved by: re (kib) Modified: head/sys/kern/kern_lock.c head/sys/kern/kern_mutex.c head/sys/kern/kern_rwlock.c head/sys/kern/kern_sx.c head/sys/sys/systm.h Modified: head/sys/kern/kern_lock.c ============================================================================== --- head/sys/kern/kern_lock.c Mon Aug 17 16:16:46 2009 (r196333) +++ head/sys/kern/kern_lock.c Mon Aug 17 16:17:21 2009 (r196334) @@ -334,6 +334,9 @@ lockinit(struct lock *lk, int pri, const int iflags; MPASS((flags & ~LK_INIT_MASK) == 0); + ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, + ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, + &lk->lk_lock)); iflags = LO_SLEEPABLE | LO_UPGRADABLE; if (flags & LK_CANRECURSE) Modified: head/sys/kern/kern_mutex.c ============================================================================== --- head/sys/kern/kern_mutex.c Mon Aug 17 16:16:46 2009 (r196333) +++ head/sys/kern/kern_mutex.c Mon Aug 17 16:17:21 2009 (r196334) @@ -783,8 +783,9 @@ mtx_init(struct mtx *m, const char *name MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE | MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0); - ASSERT_ATOMIC_LOAD(m->mtx_lock, ("%s: mtx_lock not aligned for %s: %p", - __func__, name, &m->mtx_lock)); + ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock, + ("%s: mtx_lock not aligned for %s: %p", __func__, name, + &m->mtx_lock)); #ifdef MUTEX_DEBUG /* Diagnostic and error correction */ Modified: head/sys/kern/kern_rwlock.c ============================================================================== --- head/sys/kern/kern_rwlock.c Mon Aug 17 16:16:46 2009 (r196333) +++ head/sys/kern/kern_rwlock.c Mon Aug 17 16:17:21 2009 (r196334) @@ -174,8 +174,9 @@ rw_init_flags(struct rwlock *rw, const c MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET | RW_RECURSE)) == 0); - ASSERT_ATOMIC_LOAD(rw->rw_lock, ("%s: rw_lock not aligned for %s: %p", - __func__, name, &rw->rw_lock)); + ASSERT_ATOMIC_LOAD_PTR(rw->rw_lock, + ("%s: rw_lock not aligned for %s: %p", __func__, name, + &rw->rw_lock)); flags = LO_UPGRADABLE; if (opts & RW_DUPOK) Modified: head/sys/kern/kern_sx.c ============================================================================== --- head/sys/kern/kern_sx.c Mon Aug 17 16:16:46 2009 (r196333) +++ head/sys/kern/kern_sx.c Mon Aug 17 16:17:21 2009 (r196334) @@ -205,8 +205,9 @@ sx_init_flags(struct sx *sx, const char MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | SX_NOPROFILE | SX_NOADAPTIVE)) == 0); - ASSERT_ATOMIC_LOAD(sx->sx_lock, ("%s: sx_lock not aligned for %s: %p", - __func__, description, &sx->sx_lock)); + ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, + ("%s: sx_lock not aligned for %s: %p", __func__, description, + &sx->sx_lock)); flags = LO_SLEEPABLE | LO_UPGRADABLE; if (opts & SX_DUPOK) Modified: head/sys/sys/systm.h ============================================================================== --- head/sys/sys/systm.h Mon Aug 17 16:16:46 2009 (r196333) +++ head/sys/sys/systm.h Mon Aug 17 16:17:21 2009 (r196334) @@ -89,9 +89,16 @@ extern int maxusers; /* system tune hin #define __CTASSERT(x, y) typedef char __assert ## y[(x) ? 1 : -1] #endif -#define ASSERT_ATOMIC_LOAD(var,msg) \ - KASSERT(sizeof(var) <= sizeof(uintptr_t) && \ - ALIGN(&(var)) == (uintptr_t)&(var), msg) +/* + * Assert that a pointer can be loaded from memory atomically. + * + * This assertion enforces stronger alignment than necessary. For example, + * on some architectures, atomicity for unaligned loads will depend on + * whether or not the load spans multiple cache lines. + */ +#define ASSERT_ATOMIC_LOAD_PTR(var, msg) \ + KASSERT(sizeof(var) == sizeof(void *) && \ + ((uintptr_t)&(var) & (sizeof(void *) - 1)) == 0, msg) /* * XXX the hints declarations are even more misplaced than most declarations
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