Acked-by: Joe Stringer <joestrin...@nicira.com>
On 16 January 2014 10:07, Ben Pfaff <b...@nicira.com> wrote:
> With glibc, rwlocks by default allow recursive read-locking even if a
> thread is blocked waiting for the write-lock. POSIX allows such attempts
> to deadlock, and it appears that the libc used in NetBSD, at least, does
> deadlock. The netdev_class_rwlock is in fact acquired recursively in this
> way, which is a bug. This commit fixes the problem by switching to a
> recursive mutex. This allows for less parallelism, but according to an
> existing comment that doesn't matter here anyway.
>
> Signed-off-by: Ben Pfaff <b...@nicira.com>
> ---
> lib/netdev.c | 63
> +++++++++++++++++++++++++++++-----------------------------
> 1 file changed, 32 insertions(+), 31 deletions(-)
>
> diff --git a/lib/netdev.c b/lib/netdev.c
> index 575227c..8fd63de 100644
> --- a/lib/netdev.c
> +++ b/lib/netdev.c
> @@ -1,5 +1,5 @@
> /*
> - * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
> + * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
> *
> * Licensed under the Apache License, Version 2.0 (the "License");
> * you may not use this file except in compliance with the License.
> @@ -67,15 +67,14 @@ static struct shash netdev_shash
> OVS_GUARDED_BY(netdev_mutex)
>
> /* Protects 'netdev_classes' against insertions or deletions.
> *
> - * This is not an rwlock for performance reasons but to allow recursive
> - * acquisition when calling into providers. For example, netdev_run()
> calls
> - * into provider 'run' functions, which might reasonably want to call one
> of
> - * the netdev functions that takes netdev_class_rwlock read-only. */
> -static struct ovs_rwlock netdev_class_rwlock OVS_ACQ_BEFORE(netdev_mutex)
> - = OVS_RWLOCK_INITIALIZER;
> + * This is a recursive mutex to allow recursive acquisition when calling
> into
> + * providers. For example, netdev_run() calls into provider 'run'
> functions,
> + * which might reasonably want to call one of the netdev functions that
> takes
> + * netdev_class_mutex. */
> +static struct ovs_mutex netdev_class_mutex OVS_ACQ_BEFORE(netdev_mutex);
>
> /* Contains 'struct netdev_registered_class'es. */
> -static struct hmap netdev_classes OVS_GUARDED_BY(netdev_class_rwlock)
> +static struct hmap netdev_classes OVS_GUARDED_BY(netdev_class_mutex)
> = HMAP_INITIALIZER(&netdev_classes);
>
> struct netdev_registered_class {
> @@ -93,11 +92,13 @@ void update_device_args(struct netdev *, const struct
> shash *args);
>
> static void
> netdev_initialize(void)
> - OVS_EXCLUDED(netdev_class_rwlock, netdev_mutex)
> + OVS_EXCLUDED(netdev_class_mutex, netdev_mutex)
> {
> static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
>
> if (ovsthread_once_start(&once)) {
> + ovs_mutex_init_recursive(&netdev_class_mutex);
> +
> fatal_signal_add_hook(restore_all_flags, NULL, NULL, true);
> netdev_vport_patch_register();
>
> @@ -122,17 +123,17 @@ netdev_initialize(void)
> * main poll loop. */
> void
> netdev_run(void)
> - OVS_EXCLUDED(netdev_class_rwlock, netdev_mutex)
> + OVS_EXCLUDED(netdev_class_mutex, netdev_mutex)
> {
> struct netdev_registered_class *rc;
>
> - ovs_rwlock_rdlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> HMAP_FOR_EACH (rc, hmap_node, &netdev_classes) {
> if (rc->class->run) {
> rc->class->run();
> }
> }
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
> }
>
> /* Arranges for poll_block() to wake up when netdev_run() needs to be
> called.
> @@ -141,22 +142,22 @@ netdev_run(void)
> * main poll loop. */
> void
> netdev_wait(void)
> - OVS_EXCLUDED(netdev_class_rwlock, netdev_mutex)
> + OVS_EXCLUDED(netdev_class_mutex, netdev_mutex)
> {
> struct netdev_registered_class *rc;
>
> - ovs_rwlock_rdlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> HMAP_FOR_EACH (rc, hmap_node, &netdev_classes) {
> if (rc->class->wait) {
> rc->class->wait();
> }
> }
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
> }
>
> static struct netdev_registered_class *
> netdev_lookup_class(const char *type)
> - OVS_REQ_RDLOCK(netdev_class_rwlock)
> + OVS_REQ_RDLOCK(netdev_class_mutex)
> {
> struct netdev_registered_class *rc;
>
> @@ -173,11 +174,11 @@ netdev_lookup_class(const char *type)
> * registration, new netdevs of that type can be opened using
> netdev_open(). */
> int
> netdev_register_provider(const struct netdev_class *new_class)
> - OVS_EXCLUDED(netdev_class_rwlock, netdev_mutex)
> + OVS_EXCLUDED(netdev_class_mutex, netdev_mutex)
> {
> int error;
>
> - ovs_rwlock_wrlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> if (netdev_lookup_class(new_class->type)) {
> VLOG_WARN("attempted to register duplicate netdev provider: %s",
> new_class->type);
> @@ -197,7 +198,7 @@ netdev_register_provider(const struct netdev_class
> *new_class)
> new_class->type, ovs_strerror(error));
> }
> }
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
>
> return error;
> }
> @@ -207,12 +208,12 @@ netdev_register_provider(const struct netdev_class
> *new_class)
> * new netdevs of that type cannot be opened using netdev_open(). */
> int
> netdev_unregister_provider(const char *type)
> - OVS_EXCLUDED(netdev_class_rwlock, netdev_mutex)
> + OVS_EXCLUDED(netdev_class_mutex, netdev_mutex)
> {
> struct netdev_registered_class *rc;
> int error;
>
> - ovs_rwlock_wrlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> rc = netdev_lookup_class(type);
> if (!rc) {
> VLOG_WARN("attempted to unregister a netdev provider that is not "
> @@ -233,7 +234,7 @@ netdev_unregister_provider(const char *type)
> error = EBUSY;
> }
> }
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
>
> return error;
> }
> @@ -249,11 +250,11 @@ netdev_enumerate_types(struct sset *types)
> netdev_initialize();
> sset_clear(types);
>
> - ovs_rwlock_rdlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> HMAP_FOR_EACH (rc, hmap_node, &netdev_classes) {
> sset_add(types, rc->class->type);
> }
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
> }
>
> /* Check that the network device name is not the same as any of the
> registered
> @@ -269,15 +270,15 @@ netdev_is_reserved_name(const char *name)
>
> netdev_initialize();
>
> - ovs_rwlock_rdlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> HMAP_FOR_EACH (rc, hmap_node, &netdev_classes) {
> const char *dpif_port =
> netdev_vport_class_get_dpif_port(rc->class);
> if (dpif_port && !strcmp(dpif_port, name)) {
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
> return true;
> }
> }
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
>
> if (!strncmp(name, "ovs-", 4)) {
> struct sset types;
> @@ -313,7 +314,7 @@ netdev_open(const char *name, const char *type, struct
> netdev **netdevp)
>
> netdev_initialize();
>
> - ovs_rwlock_rdlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> ovs_mutex_lock(&netdev_mutex);
> netdev = shash_find_data(&netdev_shash, name);
> if (!netdev) {
> @@ -354,7 +355,7 @@ netdev_open(const char *name, const char *type, struct
> netdev **netdevp)
> }
>
> ovs_mutex_unlock(&netdev_mutex);
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
>
> if (!error) {
> netdev->ref_cnt++;
> @@ -460,11 +461,11 @@ netdev_unref(struct netdev *dev)
> dev->netdev_class->dealloc(dev);
> ovs_mutex_unlock(&netdev_mutex);
>
> - ovs_rwlock_rdlock(&netdev_class_rwlock);
> + ovs_mutex_lock(&netdev_class_mutex);
> rc = netdev_lookup_class(class->type);
> atomic_sub(&rc->ref_cnt, 1, &old_ref_cnt);
> ovs_assert(old_ref_cnt > 0);
> - ovs_rwlock_unlock(&netdev_class_rwlock);
> + ovs_mutex_unlock(&netdev_class_mutex);
> } else {
> ovs_mutex_unlock(&netdev_mutex);
> }
> --
> 1.7.10.4
>
> _______________________________________________
> dev mailing list
> dev@openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev
>
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