Date: Fri, 28 Aug 2009 22:30:55 +0000 (UTC) From: Marko Zec <zec@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r196633 - head/sys/net Message-ID: <200908282230.n7SMUtP6038313@svn.freebsd.org>
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Author: zec Date: Fri Aug 28 22:30:55 2009 New Revision: 196633 URL: http://svn.freebsd.org/changeset/base/196633 Log: Introduce a separate sx lock for protecting lists of vnet sysinit 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 Modified: head/sys/net/vnet.c Modified: head/sys/net/vnet.c ============================================================================== --- head/sys/net/vnet.c Fri Aug 28 21:14:04 2009 (r196632) +++ head/sys/net/vnet.c Fri Aug 28 22:30:55 2009 (r196633) @@ -182,14 +182,21 @@ static VNET_DEFINE(char, modspace[VNET_M /* * 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
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