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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