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Introduce a separate sx lock for protecting lists of vnet sysinit

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and sysuninit handlers.

Previously, sx_vnet, which is a lock designated for protecting
the vnet list, was (ab)used for protecting vnet sysinit / sysuninit
handler lists as well.  Holding exclusively the sx_vnet lock while
invoking sysinit and / or sysuninit handlers turned out to be
problematic, since some of the handlers may attempt to wake up
another thread and wait for it to walk over the vnet list, hence
acquire a shared lock on sx_vnet, which in turn leads to a deadlock.
Protecting vnet sysinit / sysuninit lists with a separate lock
mitigates this issue, which was first observed with
flowtable_flush() / flowtable_cleaner() in sys/net/flowtable.c.

Reviewed by:	rwatson, jhb
MFC after:	3 days
This commit is contained in:
Marko Zec 2009-08-28 22:30:55 +00:00
parent 2fa8c8d21e
commit a99fcfd4ca
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=196633
1 changed files with 26 additions and 20 deletions
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46
sys/net/vnet.c
View file

@ -182,14 +182,21 @@ static VNET_DEFINE(char, modspace[VNET_MODMIN]);
/*
* Global lists of subsystem constructor and destructors for vnets. They are
* registered via VNET_SYSINIT() and VNET_SYSUNINIT(). The lists are
* protected by the vnet_sxlock global lock.
* registered via VNET_SYSINIT() and VNET_SYSUNINIT(). Both lists are
* protected by the vnet_sysinit_sxlock global lock.
*/
static TAILQ_HEAD(vnet_sysinit_head, vnet_sysinit) vnet_constructors =
TAILQ_HEAD_INITIALIZER(vnet_constructors);
static TAILQ_HEAD(vnet_sysuninit_head, vnet_sysinit) vnet_destructors =
TAILQ_HEAD_INITIALIZER(vnet_destructors);
struct sx vnet_sysinit_sxlock;
#define VNET_SYSINIT_WLOCK() sx_xlock(&vnet_sysinit_sxlock);
#define VNET_SYSINIT_WUNLOCK() sx_xunlock(&vnet_sysinit_sxlock);
#define VNET_SYSINIT_RLOCK() sx_slock(&vnet_sysinit_sxlock);
#define VNET_SYSINIT_RUNLOCK() sx_sunlock(&vnet_sysinit_sxlock);
struct vnet_data_free {
uintptr_t vnd_start;
int vnd_len;
@ -228,12 +235,10 @@ vnet_alloc(void)
/* Initialize / attach vnet module instances. */
CURVNET_SET_QUIET(vnet);
sx_xlock(&vnet_sxlock);
vnet_sysinit();
CURVNET_RESTORE();
rw_wlock(&vnet_rwlock);
VNET_LIST_WLOCK();
LIST_INSERT_HEAD(&vnet_head, vnet, vnet_le);
VNET_LIST_WUNLOCK();
@ -253,7 +258,7 @@ vnet_destroy(struct vnet *vnet)
VNET_LIST_WLOCK();
LIST_REMOVE(vnet, vnet_le);
rw_wunlock(&vnet_rwlock);
VNET_LIST_WUNLOCK();
CURVNET_SET_QUIET(vnet);
@ -264,8 +269,6 @@ vnet_destroy(struct vnet *vnet)
}
vnet_sysuninit();
sx_xunlock(&vnet_sxlock);
CURVNET_RESTORE();
/*
@ -287,6 +290,7 @@ vnet_init_prelink(void *arg)
rw_init(&vnet_rwlock, "vnet_rwlock");
sx_init(&vnet_sxlock, "vnet_sxlock");
sx_init(&vnet_sysinit_sxlock, "vnet_sysinit_sxlock");
LIST_INIT(&vnet_head);
}
SYSINIT(vnet_init_prelink, SI_SUB_VNET_PRELINK, SI_ORDER_FIRST,
@ -494,7 +498,7 @@ vnet_register_sysinit(void *arg)
KASSERT(vs->subsystem > SI_SUB_VNET, ("vnet sysinit too early"));
/* Add the constructor to the global list of vnet constructors. */
sx_xlock(&vnet_sxlock);
VNET_SYSINIT_WLOCK();
TAILQ_FOREACH(vs2, &vnet_constructors, link) {
if (vs2->subsystem > vs->subsystem)
break;
@ -515,7 +519,7 @@ vnet_register_sysinit(void *arg)
vs->func(vs->arg);
CURVNET_RESTORE();
}
sx_xunlock(&vnet_sxlock);
VNET_SYSINIT_WUNLOCK();
}
void
@ -526,9 +530,9 @@ vnet_deregister_sysinit(void *arg)
vs = arg;
/* Remove the constructor from the global list of vnet constructors. */
sx_xlock(&vnet_sxlock);
VNET_SYSINIT_WLOCK();
TAILQ_REMOVE(&vnet_constructors, vs, link);
sx_xunlock(&vnet_sxlock);
VNET_SYSINIT_WUNLOCK();
}
void
@ -539,7 +543,7 @@ vnet_register_sysuninit(void *arg)
vs = arg;
/* Add the destructor to the global list of vnet destructors. */
sx_xlock(&vnet_sxlock);
VNET_SYSINIT_WLOCK();
TAILQ_FOREACH(vs2, &vnet_destructors, link) {
if (vs2->subsystem > vs->subsystem)
break;
@ -550,7 +554,7 @@ vnet_register_sysuninit(void *arg)
TAILQ_INSERT_BEFORE(vs2, vs, link);
else
TAILQ_INSERT_TAIL(&vnet_destructors, vs, link);
sx_xunlock(&vnet_sxlock);
VNET_SYSINIT_WUNLOCK();
}
void
@ -565,7 +569,7 @@ vnet_deregister_sysuninit(void *arg)
* Invoke the destructor on all the existing vnets when it is
* deregistered.
*/
sx_xlock(&vnet_sxlock);
VNET_SYSINIT_WLOCK();
VNET_FOREACH(vnet) {
CURVNET_SET_QUIET(vnet);
vs->func(vs->arg);
@ -574,40 +578,42 @@ vnet_deregister_sysuninit(void *arg)
/* Remove the destructor from the global list of vnet destructors. */
TAILQ_REMOVE(&vnet_destructors, vs, link);
sx_xunlock(&vnet_sxlock);
VNET_SYSINIT_WUNLOCK();
}
/*
* Invoke all registered vnet constructors on the current vnet. Used during
* vnet construction. The caller is responsible for ensuring the new vnet is
* the current vnet and that the vnet_sxlock lock is locked.
* the current vnet and that the vnet_sysinit_sxlock lock is locked.
*/
void
vnet_sysinit(void)
{
struct vnet_sysinit *vs;
sx_assert(&vnet_sxlock, SA_LOCKED);
VNET_SYSINIT_RLOCK();
TAILQ_FOREACH(vs, &vnet_constructors, link) {
vs->func(vs->arg);
}
VNET_SYSINIT_RUNLOCK();
}
/*
* Invoke all registered vnet destructors on the current vnet. Used during
* vnet destruction. The caller is responsible for ensuring the dying vnet
* is the current vnet and that the vnet_sxlock lock is locked.
* the current vnet and that the vnet_sysinit_sxlock lock is locked.
*/
void
vnet_sysuninit(void)
{
struct vnet_sysinit *vs;
sx_assert(&vnet_sxlock, SA_LOCKED);
VNET_SYSINIT_RLOCK();
TAILQ_FOREACH_REVERSE(vs, &vnet_destructors, vnet_sysuninit_head,
link) {
vs->func(vs->arg);
}
VNET_SYSINIT_RUNLOCK();
}
#ifdef DDB