From 6b5c13b591d753c6022fbd12f8c0c0a9a07fc065 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle Date: Fri, 7 Jul 2023 12:56:20 +0200 Subject: [PATCH 1/3] s390/ism: Fix locking for forwarding of IRQs and events to clients The clients array references all registered clients and is protected by the clients_lock. Besides its use as general list of clients the clients array is accessed in ism_handle_irq() to forward ISM device events to clients. While the clients_lock is taken in the IRQ handler when calling handle_event() it is however incorrectly not held during the client->handle_irq() call and for the preceding clients[] access leaving it unprotected against concurrent client (un-)registration. Furthermore the accesses to ism->sba_client_arr[] in ism_register_dmb() and ism_unregister_dmb() are not protected by any lock. This is especially problematic as the client ID from the ism->sba_client_arr[] is not checked against NO_CLIENT and neither is the client pointer checked. Instead of expanding the use of the clients_lock further add a separate array in struct ism_dev which references clients subscribed to the device's events and IRQs. This array is protected by ism->lock which is already taken in ism_handle_irq() and can be taken outside the IRQ handler when adding/removing subscribers or the accessing ism->sba_client_arr[]. This also means that the clients_lock is no longer taken in IRQ context. Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") Signed-off-by: Niklas Schnelle Reviewed-by: Alexandra Winter Signed-off-by: David S. Miller --- drivers/s390/net/ism_drv.c | 44 +++++++++++++++++++++++++++++++------- include/linux/ism.h | 1 + 2 files changed, 37 insertions(+), 8 deletions(-) diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c index 9b5fccdbc7d6..b664e4a08645 100644 --- a/drivers/s390/net/ism_drv.c +++ b/drivers/s390/net/ism_drv.c @@ -47,6 +47,15 @@ static struct ism_dev_list ism_dev_list = { .mutex = __MUTEX_INITIALIZER(ism_dev_list.mutex), }; +static void ism_setup_forwarding(struct ism_client *client, struct ism_dev *ism) +{ + unsigned long flags; + + spin_lock_irqsave(&ism->lock, flags); + ism->subs[client->id] = client; + spin_unlock_irqrestore(&ism->lock, flags); +} + int ism_register_client(struct ism_client *client) { struct ism_dev *ism; @@ -71,6 +80,7 @@ int ism_register_client(struct ism_client *client) list_for_each_entry(ism, &ism_dev_list.list, list) { ism->priv[i] = NULL; client->add(ism); + ism_setup_forwarding(client, ism); } } mutex_unlock(&ism_dev_list.mutex); @@ -92,6 +102,9 @@ int ism_unregister_client(struct ism_client *client) max_client--; spin_unlock_irqrestore(&clients_lock, flags); list_for_each_entry(ism, &ism_dev_list.list, list) { + spin_lock_irqsave(&ism->lock, flags); + /* Stop forwarding IRQs and events */ + ism->subs[client->id] = NULL; for (int i = 0; i < ISM_NR_DMBS; ++i) { if (ism->sba_client_arr[i] == client->id) { pr_err("%s: attempt to unregister client '%s'" @@ -101,6 +114,7 @@ int ism_unregister_client(struct ism_client *client) goto out; } } + spin_unlock_irqrestore(&ism->lock, flags); } out: mutex_unlock(&ism_dev_list.mutex); @@ -328,6 +342,7 @@ int ism_register_dmb(struct ism_dev *ism, struct ism_dmb *dmb, struct ism_client *client) { union ism_reg_dmb cmd; + unsigned long flags; int ret; ret = ism_alloc_dmb(ism, dmb); @@ -351,7 +366,9 @@ int ism_register_dmb(struct ism_dev *ism, struct ism_dmb *dmb, goto out; } dmb->dmb_tok = cmd.response.dmb_tok; + spin_lock_irqsave(&ism->lock, flags); ism->sba_client_arr[dmb->sba_idx - ISM_DMB_BIT_OFFSET] = client->id; + spin_unlock_irqrestore(&ism->lock, flags); out: return ret; } @@ -360,6 +377,7 @@ EXPORT_SYMBOL_GPL(ism_register_dmb); int ism_unregister_dmb(struct ism_dev *ism, struct ism_dmb *dmb) { union ism_unreg_dmb cmd; + unsigned long flags; int ret; memset(&cmd, 0, sizeof(cmd)); @@ -368,7 +386,9 @@ int ism_unregister_dmb(struct ism_dev *ism, struct ism_dmb *dmb) cmd.request.dmb_tok = dmb->dmb_tok; + spin_lock_irqsave(&ism->lock, flags); ism->sba_client_arr[dmb->sba_idx - ISM_DMB_BIT_OFFSET] = NO_CLIENT; + spin_unlock_irqrestore(&ism->lock, flags); ret = ism_cmd(ism, &cmd); if (ret && ret != ISM_ERROR) @@ -491,6 +511,7 @@ static u16 ism_get_chid(struct ism_dev *ism) static void ism_handle_event(struct ism_dev *ism) { struct ism_event *entry; + struct ism_client *clt; int i; while ((ism->ieq_idx + 1) != READ_ONCE(ism->ieq->header.idx)) { @@ -499,21 +520,21 @@ static void ism_handle_event(struct ism_dev *ism) entry = &ism->ieq->entry[ism->ieq_idx]; debug_event(ism_debug_info, 2, entry, sizeof(*entry)); - spin_lock(&clients_lock); - for (i = 0; i < max_client; ++i) - if (clients[i]) - clients[i]->handle_event(ism, entry); - spin_unlock(&clients_lock); + for (i = 0; i < max_client; ++i) { + clt = ism->subs[i]; + if (clt) + clt->handle_event(ism, entry); + } } } static irqreturn_t ism_handle_irq(int irq, void *data) { struct ism_dev *ism = data; - struct ism_client *clt; unsigned long bit, end; unsigned long *bv; u16 dmbemask; + u8 client_id; bv = (void *) &ism->sba->dmb_bits[ISM_DMB_WORD_OFFSET]; end = sizeof(ism->sba->dmb_bits) * BITS_PER_BYTE - ISM_DMB_BIT_OFFSET; @@ -530,8 +551,10 @@ static irqreturn_t ism_handle_irq(int irq, void *data) dmbemask = ism->sba->dmbe_mask[bit + ISM_DMB_BIT_OFFSET]; ism->sba->dmbe_mask[bit + ISM_DMB_BIT_OFFSET] = 0; barrier(); - clt = clients[ism->sba_client_arr[bit]]; - clt->handle_irq(ism, bit + ISM_DMB_BIT_OFFSET, dmbemask); + client_id = ism->sba_client_arr[bit]; + if (unlikely(client_id == NO_CLIENT || !ism->subs[client_id])) + continue; + ism->subs[client_id]->handle_irq(ism, bit + ISM_DMB_BIT_OFFSET, dmbemask); } if (ism->sba->e) { @@ -554,6 +577,7 @@ static void ism_dev_add_work_func(struct work_struct *work) add_work); client->add(client->tgt_ism); + ism_setup_forwarding(client, client->tgt_ism); atomic_dec(&client->tgt_ism->add_dev_cnt); wake_up(&client->tgt_ism->waitq); } @@ -691,7 +715,11 @@ static void ism_dev_remove_work_func(struct work_struct *work) { struct ism_client *client = container_of(work, struct ism_client, remove_work); + unsigned long flags; + spin_lock_irqsave(&client->tgt_ism->lock, flags); + client->tgt_ism->subs[client->id] = NULL; + spin_unlock_irqrestore(&client->tgt_ism->lock, flags); client->remove(client->tgt_ism); atomic_dec(&client->tgt_ism->free_clients_cnt); wake_up(&client->tgt_ism->waitq); diff --git a/include/linux/ism.h b/include/linux/ism.h index ea2bcdae7401..5160d47e5ea9 100644 --- a/include/linux/ism.h +++ b/include/linux/ism.h @@ -44,6 +44,7 @@ struct ism_dev { u64 local_gid; int ieq_idx; + struct ism_client *subs[MAX_CLIENTS]; atomic_t free_clients_cnt; atomic_t add_dev_cnt; wait_queue_head_t waitq; From 76631ffa2fd2d45bae5ad717eef716b94144e0e7 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle Date: Fri, 7 Jul 2023 12:56:21 +0200 Subject: [PATCH 2/3] s390/ism: Fix and simplify add()/remove() callback handling Previously the clients_lock was protecting the clients array against concurrent addition/removal of clients but was also accessed from IRQ context. This meant that it had to be a spinlock and that the add() and remove() callbacks in which clients need to do allocation and take mutexes can't be called under the clients_lock. To work around this these callbacks were moved to workqueues. This not only introduced significant complexity but is also subtly broken in at least one way. In ism_dev_init() and ism_dev_exit() clients[i]->tgt_ism is used to communicate the added/removed ISM device to the work function. While write access to client[i]->tgt_ism is protected by the clients_lock and the code waits that there is no pending add/remove work before and after setting clients[i]->tgt_ism this is not enough. The problem is that the wait happens based on per ISM device counters. Thus a concurrent ism_dev_init()/ism_dev_exit() for a different ISM device may overwrite a clients[i]->tgt_ism between unlocking the clients_lock and the subsequent wait for the work to finnish. Thankfully with the clients_lock no longer held in IRQ context it can be turned into a mutex which can be held during the calls to add()/remove() completely removing the need for the workqueues and the associated broken housekeeping including the per ISM device counters and the clients[i]->tgt_ism. Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") Signed-off-by: Niklas Schnelle Signed-off-by: David S. Miller --- drivers/s390/net/ism_drv.c | 90 +++++++++++--------------------------- include/linux/ism.h | 6 --- 2 files changed, 26 insertions(+), 70 deletions(-) diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c index b664e4a08645..54091b7aea16 100644 --- a/drivers/s390/net/ism_drv.c +++ b/drivers/s390/net/ism_drv.c @@ -36,7 +36,7 @@ static const struct smcd_ops ism_ops; static struct ism_client *clients[MAX_CLIENTS]; /* use an array rather than */ /* a list for fast mapping */ static u8 max_client; -static DEFINE_SPINLOCK(clients_lock); +static DEFINE_MUTEX(clients_lock); struct ism_dev_list { struct list_head list; struct mutex mutex; /* protects ism device list */ @@ -59,11 +59,10 @@ static void ism_setup_forwarding(struct ism_client *client, struct ism_dev *ism) int ism_register_client(struct ism_client *client) { struct ism_dev *ism; - unsigned long flags; int i, rc = -ENOSPC; mutex_lock(&ism_dev_list.mutex); - spin_lock_irqsave(&clients_lock, flags); + mutex_lock(&clients_lock); for (i = 0; i < MAX_CLIENTS; ++i) { if (!clients[i]) { clients[i] = client; @@ -74,7 +73,8 @@ int ism_register_client(struct ism_client *client) break; } } - spin_unlock_irqrestore(&clients_lock, flags); + mutex_unlock(&clients_lock); + if (i < MAX_CLIENTS) { /* initialize with all devices that we got so far */ list_for_each_entry(ism, &ism_dev_list.list, list) { @@ -96,11 +96,11 @@ int ism_unregister_client(struct ism_client *client) int rc = 0; mutex_lock(&ism_dev_list.mutex); - spin_lock_irqsave(&clients_lock, flags); + mutex_lock(&clients_lock); clients[client->id] = NULL; if (client->id + 1 == max_client) max_client--; - spin_unlock_irqrestore(&clients_lock, flags); + mutex_unlock(&clients_lock); list_for_each_entry(ism, &ism_dev_list.list, list) { spin_lock_irqsave(&ism->lock, flags); /* Stop forwarding IRQs and events */ @@ -571,21 +571,9 @@ static u64 ism_get_local_gid(struct ism_dev *ism) return ism->local_gid; } -static void ism_dev_add_work_func(struct work_struct *work) -{ - struct ism_client *client = container_of(work, struct ism_client, - add_work); - - client->add(client->tgt_ism); - ism_setup_forwarding(client, client->tgt_ism); - atomic_dec(&client->tgt_ism->add_dev_cnt); - wake_up(&client->tgt_ism->waitq); -} - static int ism_dev_init(struct ism_dev *ism) { struct pci_dev *pdev = ism->pdev; - unsigned long flags; int i, ret; ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSI); @@ -618,25 +606,16 @@ static int ism_dev_init(struct ism_dev *ism) /* hardware is V2 capable */ ism_create_system_eid(); - init_waitqueue_head(&ism->waitq); - atomic_set(&ism->free_clients_cnt, 0); - atomic_set(&ism->add_dev_cnt, 0); - - wait_event(ism->waitq, !atomic_read(&ism->add_dev_cnt)); - spin_lock_irqsave(&clients_lock, flags); - for (i = 0; i < max_client; ++i) - if (clients[i]) { - INIT_WORK(&clients[i]->add_work, - ism_dev_add_work_func); - clients[i]->tgt_ism = ism; - atomic_inc(&ism->add_dev_cnt); - schedule_work(&clients[i]->add_work); - } - spin_unlock_irqrestore(&clients_lock, flags); - - wait_event(ism->waitq, !atomic_read(&ism->add_dev_cnt)); - mutex_lock(&ism_dev_list.mutex); + mutex_lock(&clients_lock); + for (i = 0; i < max_client; ++i) { + if (clients[i]) { + clients[i]->add(ism); + ism_setup_forwarding(clients[i], ism); + } + } + mutex_unlock(&clients_lock); + list_add(&ism->list, &ism_dev_list.list); mutex_unlock(&ism_dev_list.mutex); @@ -711,40 +690,24 @@ err_dev: return ret; } -static void ism_dev_remove_work_func(struct work_struct *work) -{ - struct ism_client *client = container_of(work, struct ism_client, - remove_work); - unsigned long flags; - - spin_lock_irqsave(&client->tgt_ism->lock, flags); - client->tgt_ism->subs[client->id] = NULL; - spin_unlock_irqrestore(&client->tgt_ism->lock, flags); - client->remove(client->tgt_ism); - atomic_dec(&client->tgt_ism->free_clients_cnt); - wake_up(&client->tgt_ism->waitq); -} - -/* Callers must hold ism_dev_list.mutex */ static void ism_dev_exit(struct ism_dev *ism) { struct pci_dev *pdev = ism->pdev; unsigned long flags; int i; - wait_event(ism->waitq, !atomic_read(&ism->free_clients_cnt)); - spin_lock_irqsave(&clients_lock, flags); + spin_lock_irqsave(&ism->lock, flags); for (i = 0; i < max_client; ++i) - if (clients[i]) { - INIT_WORK(&clients[i]->remove_work, - ism_dev_remove_work_func); - clients[i]->tgt_ism = ism; - atomic_inc(&ism->free_clients_cnt); - schedule_work(&clients[i]->remove_work); - } - spin_unlock_irqrestore(&clients_lock, flags); + ism->subs[i] = NULL; + spin_unlock_irqrestore(&ism->lock, flags); - wait_event(ism->waitq, !atomic_read(&ism->free_clients_cnt)); + mutex_lock(&ism_dev_list.mutex); + mutex_lock(&clients_lock); + for (i = 0; i < max_client; ++i) { + if (clients[i]) + clients[i]->remove(ism); + } + mutex_unlock(&clients_lock); if (SYSTEM_EID.serial_number[0] != '0' || SYSTEM_EID.type[0] != '0') @@ -755,15 +718,14 @@ static void ism_dev_exit(struct ism_dev *ism) kfree(ism->sba_client_arr); pci_free_irq_vectors(pdev); list_del_init(&ism->list); + mutex_unlock(&ism_dev_list.mutex); } static void ism_remove(struct pci_dev *pdev) { struct ism_dev *ism = dev_get_drvdata(&pdev->dev); - mutex_lock(&ism_dev_list.mutex); ism_dev_exit(ism); - mutex_unlock(&ism_dev_list.mutex); pci_release_mem_regions(pdev); pci_disable_device(pdev); diff --git a/include/linux/ism.h b/include/linux/ism.h index 5160d47e5ea9..9a4c204df3da 100644 --- a/include/linux/ism.h +++ b/include/linux/ism.h @@ -45,9 +45,6 @@ struct ism_dev { int ieq_idx; struct ism_client *subs[MAX_CLIENTS]; - atomic_t free_clients_cnt; - atomic_t add_dev_cnt; - wait_queue_head_t waitq; }; struct ism_event { @@ -69,9 +66,6 @@ struct ism_client { */ void (*handle_irq)(struct ism_dev *dev, unsigned int bit, u16 dmbemask); /* Private area - don't touch! */ - struct work_struct remove_work; - struct work_struct add_work; - struct ism_dev *tgt_ism; u8 id; }; From 266deeea34ffd28c6b6a63edf2af9b5a07161c24 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle Date: Fri, 7 Jul 2023 12:56:22 +0200 Subject: [PATCH 3/3] s390/ism: Do not unregister clients with registered DMBs When ism_unregister_client() is called but the client still has DMBs registered it returns -EBUSY and prints an error. This only happens after the client has already been unregistered however. This is unexpected as the unregister claims to have failed. Furthermore as this implies a client bug a WARN() is more appropriate. Thus move the deregistration after the check and use WARN(). Fixes: 89e7d2ba61b7 ("net/ism: Add new API for client registration") Signed-off-by: Niklas Schnelle Signed-off-by: David S. Miller --- drivers/s390/net/ism_drv.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c index 54091b7aea16..6df7f377d2f9 100644 --- a/drivers/s390/net/ism_drv.c +++ b/drivers/s390/net/ism_drv.c @@ -96,29 +96,32 @@ int ism_unregister_client(struct ism_client *client) int rc = 0; mutex_lock(&ism_dev_list.mutex); - mutex_lock(&clients_lock); - clients[client->id] = NULL; - if (client->id + 1 == max_client) - max_client--; - mutex_unlock(&clients_lock); list_for_each_entry(ism, &ism_dev_list.list, list) { spin_lock_irqsave(&ism->lock, flags); /* Stop forwarding IRQs and events */ ism->subs[client->id] = NULL; for (int i = 0; i < ISM_NR_DMBS; ++i) { if (ism->sba_client_arr[i] == client->id) { - pr_err("%s: attempt to unregister client '%s'" - "with registered dmb(s)\n", __func__, - client->name); + WARN(1, "%s: attempt to unregister '%s' with registered dmb(s)\n", + __func__, client->name); rc = -EBUSY; - goto out; + goto err_reg_dmb; } } spin_unlock_irqrestore(&ism->lock, flags); } -out: mutex_unlock(&ism_dev_list.mutex); + mutex_lock(&clients_lock); + clients[client->id] = NULL; + if (client->id + 1 == max_client) + max_client--; + mutex_unlock(&clients_lock); + return rc; + +err_reg_dmb: + spin_unlock_irqrestore(&ism->lock, flags); + mutex_unlock(&ism_dev_list.mutex); return rc; } EXPORT_SYMBOL_GPL(ism_unregister_client);