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Add some KASSERTs valid if WITNESS is defined to verify that the mbuf

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allocation routines are being called safely. Since we drop our relevant
mbuf mutex and acquire Giant before we call kmem_malloc(), we have
to make sure that this does not pave the way for a fatal lock order
reversal. Check that either Giant is already held (in which case it's safe
to grab it again and recurse on it) or, if Giant is not held, that no
other locks are held before we try to acquire Giant.

Similarily, add a KASSERT valid in the WITNESS case in m_reclaim() to
nail callers who end up in m_reclaim() and hold a lock.

Pointed out by: jhb
This commit is contained in:
bmilekic 2001-01-16 01:53:13 +00:00
parent 7039671ae9
commit 0c184cfc2b
1 changed files with 39 additions and 4 deletions
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43
sys/kern/uipc_mbuf.c
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@ -205,12 +205,22 @@ m_alloc_ref(nmb, how)
nbytes = round_page(nmb * sizeof(union mext_refcnt));
mtx_exit(&mcntfree.m_mtx, MTX_DEF);
#ifdef WITNESS
/*
* XXX: Make sure we don't create lock order problems.
* XXX: We'll grab Giant, but for that to be OK, make sure
* XXX: that either Giant is already held OR make sure that
* XXX: no other locks are held coming in.
* XXX: Revisit once most of the net stuff gets locks added.
*/
KASSERT(mtx_owned(&Giant) || witness_list(CURPROC) == 0,
("m_alloc_ref: Giant must be owned or no locks held"));
#endif
mtx_enter(&Giant, MTX_DEF);
if ((p = (caddr_t)kmem_malloc(mb_map, nbytes, how == M_TRYWAIT ?
M_WAITOK : M_NOWAIT)) == NULL) {
mtx_exit(&Giant, MTX_DEF);
mtx_enter(&mcntfree.m_mtx, MTX_DEF); /* XXX: We must be holding
it going out. */
mtx_enter(&mcntfree.m_mtx, MTX_DEF);
return (0);
}
mtx_exit(&Giant, MTX_DEF);
@ -264,9 +274,18 @@ m_mballoc(nmb, how)
nbytes = round_page(nmb * MSIZE);
/* XXX: The letting go of the mmbfree lock here may eventually
be moved to only be done for M_TRYWAIT calls to kmem_malloc() */
mtx_exit(&mmbfree.m_mtx, MTX_DEF);
#ifdef WITNESS
/*
* XXX: Make sure we don't create lock order problems.
* XXX: We'll grab Giant, but for that to be OK, make sure
* XXX: that either Giant is already held OR make sure that
* XXX: no other locks are held coming in.
* XXX: Revisit once most of the net stuff gets locks added.
*/
KASSERT(mtx_owned(&Giant) || witness_list(CURPROC) == 0,
("m_mballoc: Giant must be owned or no locks held"));
#endif
mtx_enter(&Giant, MTX_DEF);
p = (caddr_t)kmem_malloc(mb_map, nbytes, M_NOWAIT);
if (p == 0 && how == M_TRYWAIT) {
@ -390,6 +409,17 @@ m_clalloc(ncl, how)
npg = ncl;
mtx_exit(&mclfree.m_mtx, MTX_DEF);
#ifdef WITNESS
/*
* XXX: Make sure we don't create lock order problems.
* XXX: We'll grab Giant, but for that to be OK, make sure
* XXX: that either Giant is already held OR make sure that
* XXX: no other locks are held coming in.
* XXX: Revisit once most of the net stuff gets locks added.
*/
KASSERT(mtx_owned(&Giant) || witness_list(CURPROC) == 0,
("m_clalloc: Giant must be owned or no locks held"));
#endif
mtx_enter(&Giant, MTX_DEF);
p = (caddr_t)kmem_malloc(mb_map, ctob(npg),
how == M_TRYWAIT ? M_WAITOK : M_NOWAIT);
@ -467,6 +497,11 @@ m_reclaim()
register struct domain *dp;
register struct protosw *pr;
#ifdef WITNESS
KASSERT(witness_list(CURPROC) == 0,
("m_reclaim called with locks held"));
#endif
for (dp = domains; dp; dp = dp->dom_next)
for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
if (pr->pr_drain)