From 1c682593096a487fd9aebc079a307ff7a6d054a3 Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Tue, 18 Jun 2024 15:12:28 +0530 Subject: xen: privcmd: Switch from mutex to spinlock for irqfds irqfd_wakeup() gets EPOLLHUP, when it is called by eventfd_release() by way of wake_up_poll(&ctx->wqh, EPOLLHUP), which gets called under spin_lock_irqsave(). We can't use a mutex here as it will lead to a deadlock. Fix it by switching over to a spin lock. Reported-by: Al Viro Signed-off-by: Viresh Kumar Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/a66d7a7a9001424d432f52a9fc3931a1f345464f.1718703669.git.viresh.kumar@linaro.org Signed-off-by: Juergen Gross --- drivers/xen/privcmd.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) (limited to 'drivers/xen') diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index b9b784633c01..f4ba962de62b 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -846,7 +846,7 @@ out: #ifdef CONFIG_XEN_PRIVCMD_EVENTFD /* Irqfd support */ static struct workqueue_struct *irqfd_cleanup_wq; -static DEFINE_MUTEX(irqfds_lock); +static DEFINE_SPINLOCK(irqfds_lock); static LIST_HEAD(irqfds_list); struct privcmd_kernel_irqfd { @@ -910,9 +910,11 @@ irqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key) irqfd_inject(kirqfd); if (flags & EPOLLHUP) { - mutex_lock(&irqfds_lock); + unsigned long flags; + + spin_lock_irqsave(&irqfds_lock, flags); irqfd_deactivate(kirqfd); - mutex_unlock(&irqfds_lock); + spin_unlock_irqrestore(&irqfds_lock, flags); } return 0; @@ -930,6 +932,7 @@ irqfd_poll_func(struct file *file, wait_queue_head_t *wqh, poll_table *pt) static int privcmd_irqfd_assign(struct privcmd_irqfd *irqfd) { struct privcmd_kernel_irqfd *kirqfd, *tmp; + unsigned long flags; __poll_t events; struct fd f; void *dm_op; @@ -969,18 +972,18 @@ static int privcmd_irqfd_assign(struct privcmd_irqfd *irqfd) init_waitqueue_func_entry(&kirqfd->wait, irqfd_wakeup); init_poll_funcptr(&kirqfd->pt, irqfd_poll_func); - mutex_lock(&irqfds_lock); + spin_lock_irqsave(&irqfds_lock, flags); list_for_each_entry(tmp, &irqfds_list, list) { if (kirqfd->eventfd == tmp->eventfd) { ret = -EBUSY; - mutex_unlock(&irqfds_lock); + spin_unlock_irqrestore(&irqfds_lock, flags); goto error_eventfd; } } list_add_tail(&kirqfd->list, &irqfds_list); - mutex_unlock(&irqfds_lock); + spin_unlock_irqrestore(&irqfds_lock, flags); /* * Check if there was an event already pending on the eventfd before we @@ -1012,12 +1015,13 @@ static int privcmd_irqfd_deassign(struct privcmd_irqfd *irqfd) { struct privcmd_kernel_irqfd *kirqfd; struct eventfd_ctx *eventfd; + unsigned long flags; eventfd = eventfd_ctx_fdget(irqfd->fd); if (IS_ERR(eventfd)) return PTR_ERR(eventfd); - mutex_lock(&irqfds_lock); + spin_lock_irqsave(&irqfds_lock, flags); list_for_each_entry(kirqfd, &irqfds_list, list) { if (kirqfd->eventfd == eventfd) { @@ -1026,7 +1030,7 @@ static int privcmd_irqfd_deassign(struct privcmd_irqfd *irqfd) } } - mutex_unlock(&irqfds_lock); + spin_unlock_irqrestore(&irqfds_lock, flags); eventfd_ctx_put(eventfd); @@ -1074,13 +1078,14 @@ static int privcmd_irqfd_init(void) static void privcmd_irqfd_exit(void) { struct privcmd_kernel_irqfd *kirqfd, *tmp; + unsigned long flags; - mutex_lock(&irqfds_lock); + spin_lock_irqsave(&irqfds_lock, flags); list_for_each_entry_safe(kirqfd, tmp, &irqfds_list, list) irqfd_deactivate(kirqfd); - mutex_unlock(&irqfds_lock); + spin_unlock_irqrestore(&irqfds_lock, flags); destroy_workqueue(irqfd_cleanup_wq); } -- cgit v1.2.3