Date: Fri, 14 Aug 2009 21:46:54 +0000 (UTC) From: "Bjoern A. Zeeb" <bz@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r196226 - in head/sys: kern sys Message-ID: <200908142146.n7ELksKZ048760@svn.freebsd.org>
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Author: bz Date: Fri Aug 14 21:46:54 2009 New Revision: 196226 URL: http://svn.freebsd.org/changeset/base/196226 Log: Add a new macro to test that a variable could be loaded atomically. Check that the given variable is at most uintptr_t in size and that it is aligned. Note: ASSERT_ATOMIC_LOAD() uses ALIGN() to check for adequate alignment -- however, the function of ALIGN() is to guarantee alignment, and therefore may lead to stronger alignment enforcement than necessary for types that are smaller than sizeof(uintptr_t). Add checks to mtx, rw and sx locks init functions to detect possible breakage. This was used during debugging of the problem fixed with r196118 where a pointer was on an un-aligned address in the dpcpu area. In collaboration with: rwatson Reviewed by: rwatson Approved by: re (kib) Modified: 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_mutex.c ============================================================================== --- head/sys/kern/kern_mutex.c Fri Aug 14 21:07:41 2009 (r196225) +++ head/sys/kern/kern_mutex.c Fri Aug 14 21:46:54 2009 (r196226) @@ -783,6 +783,8 @@ 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)); #ifdef MUTEX_DEBUG /* Diagnostic and error correction */ Modified: head/sys/kern/kern_rwlock.c ============================================================================== --- head/sys/kern/kern_rwlock.c Fri Aug 14 21:07:41 2009 (r196225) +++ head/sys/kern/kern_rwlock.c Fri Aug 14 21:46:54 2009 (r196226) @@ -174,6 +174,8 @@ 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)); flags = LO_UPGRADABLE; if (opts & RW_DUPOK) Modified: head/sys/kern/kern_sx.c ============================================================================== --- head/sys/kern/kern_sx.c Fri Aug 14 21:07:41 2009 (r196225) +++ head/sys/kern/kern_sx.c Fri Aug 14 21:46:54 2009 (r196226) @@ -205,6 +205,8 @@ 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)); flags = LO_SLEEPABLE | LO_UPGRADABLE; if (opts & SX_DUPOK) Modified: head/sys/sys/systm.h ============================================================================== --- head/sys/sys/systm.h Fri Aug 14 21:07:41 2009 (r196225) +++ head/sys/sys/systm.h Fri Aug 14 21:46:54 2009 (r196226) @@ -89,6 +89,10 @@ 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) + /* * XXX the hints declarations are even more misplaced than most declarations * in this file, since they are needed in one file (per arch) and only used
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