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)
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=196226
@ -783,6 +783,8 @@ mtx_init(struct mtx *m, const char *name, const char *type, int opts)
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MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
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MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);
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ASSERT_ATOMIC_LOAD(m->mtx_lock, ("%s: mtx_lock not aligned for %s: %p",
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__func__, name, &m->mtx_lock));
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#ifdef MUTEX_DEBUG
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/* Diagnostic and error correction */
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@ -174,6 +174,8 @@ rw_init_flags(struct rwlock *rw, const char *name, int opts)
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MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET |
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RW_RECURSE)) == 0);
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ASSERT_ATOMIC_LOAD(rw->rw_lock, ("%s: rw_lock not aligned for %s: %p",
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__func__, name, &rw->rw_lock));
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flags = LO_UPGRADABLE;
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if (opts & RW_DUPOK)
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@ -205,6 +205,8 @@ sx_init_flags(struct sx *sx, const char *description, int opts)
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MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK |
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SX_NOPROFILE | SX_NOADAPTIVE)) == 0);
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ASSERT_ATOMIC_LOAD(sx->sx_lock, ("%s: sx_lock not aligned for %s: %p",
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__func__, description, &sx->sx_lock));
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flags = LO_SLEEPABLE | LO_UPGRADABLE;
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if (opts & SX_DUPOK)
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@ -89,6 +89,10 @@ extern int maxusers; /* system tune hint */
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#define __CTASSERT(x, y) typedef char __assert ## y[(x) ? 1 : -1]
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#endif
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#define ASSERT_ATOMIC_LOAD(var,msg) \
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KASSERT(sizeof(var) <= sizeof(uintptr_t) && \
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ALIGN(&(var)) == (uintptr_t)&(var), msg)
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/*
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* XXX the hints declarations are even more misplaced than most declarations
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* in this file, since they are needed in one file (per arch) and only used
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