svn commit: r291074 - in head: share/man/man9 sys/kern sys/vm
Jonathan T. Looney
jtl at FreeBSD.org
Thu Nov 19 14:04:55 UTC 2015
Author: jtl
Date: Thu Nov 19 14:04:53 2015
New Revision: 291074
URL: https://svnweb.freebsd.org/changeset/base/291074
Log:
Consistently enforce the restriction against calling malloc/free when in a
critical section.
uma_zalloc_arg()/uma_zalloc_free() may acquire a sleepable lock on the
zone. The malloc() family of functions may call uma_zalloc_arg() or
uma_zalloc_free().
The malloc(9) man page currently claims that free() will never sleep.
It also implies that the malloc() family of functions will not sleep
when called with M_NOWAIT. However, it is more correct to say that
these functions will not sleep indefinitely. Indeed, they may acquire
a sleepable lock. However, a developer may overlook this restriction
because the WITNESS check that catches attempts to call the malloc()
family of functions within a critical section is inconsistenly
applied.
This change clarifies the language of the malloc(9) man page to clarify
the restriction against calling the malloc() family of functions
while in a critical section or holding a spin lock. It also adds
KASSERTs at appropriate points to make the enforcement of this
restriction more consistent.
PR: 204633
Differential Revision: https://reviews.freebsd.org/D4197
Reviewed by: markj
Approved by: gnn (mentor)
Sponsored by: Juniper Networks
Modified:
head/share/man/man9/malloc.9
head/sys/kern/kern_malloc.c
head/sys/vm/uma_core.c
Modified: head/share/man/man9/malloc.9
==============================================================================
--- head/share/man/man9/malloc.9 Thu Nov 19 13:36:53 2015 (r291073)
+++ head/share/man/man9/malloc.9 Thu Nov 19 14:04:53 2015 (r291074)
@@ -29,7 +29,7 @@
.\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
.\" $FreeBSD$
.\"
-.Dd January 16, 2014
+.Dd November 19, 2015
.Dt MALLOC 9
.Os
.Sh NAME
@@ -227,6 +227,13 @@ may sleep when called with
.Dv M_WAITOK .
.Fn free
never sleeps.
+However,
+.Fn malloc ,
+.Fn realloc,
+.Fn reallocf
+and
+.Fn free
+may not be called in a critical section or while holding a spin lock.
.Pp
Any calls to
.Fn malloc
Modified: head/sys/kern/kern_malloc.c
==============================================================================
--- head/sys/kern/kern_malloc.c Thu Nov 19 13:36:53 2015 (r291073)
+++ head/sys/kern/kern_malloc.c Thu Nov 19 14:04:53 2015 (r291074)
@@ -476,6 +476,9 @@ malloc(unsigned long size, struct malloc
KASSERT(curthread->td_intr_nesting_level == 0,
("malloc(M_WAITOK) in interrupt context"));
+ KASSERT(curthread->td_critnest == 0,
+ ("malloc: called with spinlock or critical section held"));
+
#ifdef DEBUG_MEMGUARD
if (memguard_cmp_mtp(mtp, size)) {
va = memguard_alloc(size, flags);
@@ -542,6 +545,9 @@ free(void *addr, struct malloc_type *mtp
KASSERT(mtp->ks_magic == M_MAGIC, ("free: bad malloc type magic"));
+ KASSERT(curthread->td_critnest == 0,
+ ("free: called with spinlock or critical section held"));
+
/* free(NULL, ...) does nothing */
if (addr == NULL)
return;
@@ -605,6 +611,9 @@ realloc(void *addr, unsigned long size,
KASSERT(mtp->ks_magic == M_MAGIC,
("realloc: bad malloc type magic"));
+ KASSERT(curthread->td_critnest == 0,
+ ("realloc: called with spinlock or critical section held"));
+
/* realloc(NULL, ...) is equivalent to malloc(...) */
if (addr == NULL)
return (malloc(size, mtp, flags));
Modified: head/sys/vm/uma_core.c
==============================================================================
--- head/sys/vm/uma_core.c Thu Nov 19 13:36:53 2015 (r291073)
+++ head/sys/vm/uma_core.c Thu Nov 19 14:04:53 2015 (r291074)
@@ -2149,6 +2149,10 @@ uma_zalloc_arg(uma_zone_t zone, void *ud
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
"uma_zalloc_arg: zone \"%s\"", zone->uz_name);
}
+
+ KASSERT(curthread->td_critnest == 0,
+ ("uma_zalloc_arg: called with spinlock or critical section held"));
+
#ifdef DEBUG_MEMGUARD
if (memguard_cmp_zone(zone)) {
item = memguard_alloc(zone->uz_size, flags);
@@ -2686,6 +2690,9 @@ uma_zfree_arg(uma_zone_t zone, void *ite
CTR2(KTR_UMA, "uma_zfree_arg thread %x zone %s", curthread,
zone->uz_name);
+ KASSERT(curthread->td_critnest == 0,
+ ("uma_zfree_arg: called with spinlock or critical section held"));
+
/* uma_zfree(..., NULL) does nothing, to match free(9). */
if (item == NULL)
return;
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