From 12588ce02dd835b332952d9fece5881d943554a9 Mon Sep 17 00:00:00 2001 From: Andriy Gapon Date: Thu, 6 May 2021 21:49:37 +0300 Subject: [PATCH] PCI hot-plug: use dedicated taskqueue for device attach / detach Attaching and detaching devices can be heavy-weight and detaching can sleep waiting for events. For that reason using the system-wide single-threaded taskqueue_thread is not really appropriate. There is even a possibility for a deadlock if taskqueue_thread is used for detaching. In fact, there is an easy to reproduce deadlock involving nvme, pass and a sudden removal of an NVMe device. A pass peripheral would not release a reference on an nvme sim until pass_shutdown_kqueue() is executed via taskqueue_thread. But the taskqueue's thread is blocked in nvme_detach() -> ... -> cam_sim_free() because of the outstanding reference. MFC after: 10 days Sponsored by: CyberSecure Reviewed by: mav, imp Differential Revision: https://reviews.freebsd.org/D30144 --- sys/dev/pci/pci_pci.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/sys/dev/pci/pci_pci.c b/sys/dev/pci/pci_pci.c index 3a11d59f51fd..d6fbb06a61ac 100644 --- a/sys/dev/pci/pci_pci.c +++ b/sys/dev/pci/pci_pci.c @@ -925,6 +925,8 @@ SYSCTL_INT(_hw_pci, OID_AUTO, enable_pcie_hp, CTLFLAG_RDTUN, &pci_enable_pcie_hp, 0, "Enable support for native PCI-express HotPlug."); +TASKQUEUE_DEFINE_THREAD(pci_hp); + static void pcib_probe_hotplug(struct pcib_softc *sc) { @@ -1154,7 +1156,7 @@ pcib_pcie_hotplug_update(struct pcib_softc *sc, uint16_t val, uint16_t mask, */ if (schedule_task && (pcib_hotplug_present(sc) != 0) != (sc->child != NULL)) - taskqueue_enqueue(taskqueue_thread, &sc->pcie_hp_task); + taskqueue_enqueue(taskqueue_pci_hp, &sc->pcie_hp_task); } static void @@ -1449,7 +1451,7 @@ pcib_detach_hotplug(struct pcib_softc *sc) error = pcib_release_pcie_irq(sc); if (error) return (error); - taskqueue_drain(taskqueue_thread, &sc->pcie_hp_task); + taskqueue_drain(taskqueue_pci_hp, &sc->pcie_hp_task); callout_drain(&sc->pcie_ab_timer); callout_drain(&sc->pcie_cc_timer); callout_drain(&sc->pcie_dll_timer);