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Add a new macro to test that a variable could be loaded atomically.

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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)
This commit is contained in:
bz 2009-08-14 21:46:54 +00:00
parent d51166f15e
commit bf6acf7985
4 changed files with 10 additions and 0 deletions
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2
sys/kern/kern_mutex.c
View File

@ -783,6 +783,8 @@ mtx_init(struct mtx *m, const char *name, const char *type, int opts)
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 */

2
sys/kern/kern_rwlock.c
View File

@ -174,6 +174,8 @@ rw_init_flags(struct rwlock *rw, const char *name, int opts)
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)

2
sys/kern/kern_sx.c
View File

@ -205,6 +205,8 @@ sx_init_flags(struct sx *sx, const char *description, int opts)
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)

4
sys/sys/systm.h
View File

@ -89,6 +89,10 @@ extern int maxusers; /* system tune hint */
#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