From f652e7d2916fe2fcf9e7d709aa5b7476b431e2dd Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Fri, 11 Jan 2013 12:21:15 -0700 Subject: PCI: shpchp: Use per-slot workqueues to avoid deadlock When we have an SHPC-capable bridge with a second SHPC-capable bridge below it, pushing the upstream bridge's attention button causes a deadlock. The deadlock happens because we use the shpchp_wq workqueue to run shpchp_pushbutton_thread(), which uses shpchp_disable_slot() to remove devices below the upstream bridge. When we remove the downstream bridge, we call shpc_remove(), the shpchp driver's .remove() method. That calls flush_workqueue(shpchp_wq), which deadlocks because the shpchp_pushbutton_thread() work item is still running. This patch avoids the deadlock by creating a workqueue for every slot and removing the single shared workqueue. Here's the call path that leads to the deadlock: shpchp_queue_pushbutton_work queue_work(shpchp_wq) # shpchp_pushbutton_thread ... shpchp_pushbutton_thread shpchp_disable_slot remove_board shpchp_unconfigure_device pci_stop_and_remove_bus_device ... shpc_remove # shpchp driver .remove method hpc_release_ctlr cleanup_slots flush_workqueue(shpchp_wq) This change is based on code inspection, since we don't have hardware with this topology. Based-on-patch-by: Yijing Wang Signed-off-by: Bjorn Helgaas CC: stable@vger.kernel.org--- drivers/pci/hotplug/shpchp_ctrl.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/pci/hotplug/shpchp_ctrl.c') diff --git a/drivers/pci/hotplug/shpchp_ctrl.c b/drivers/pci/hotplug/shpchp_ctrl.c index fd2cae9eb6c2..58499277903a 100644 --- a/drivers/pci/hotplug/shpchp_ctrl.c +++ b/drivers/pci/hotplug/shpchp_ctrl.c @@ -51,7 +51,7 @@ static int queue_interrupt_event(struct slot *p_slot, u32 event_type) info->p_slot = p_slot; INIT_WORK(&info->work, interrupt_event_handler); - queue_work(shpchp_wq, &info->work); + queue_work(p_slot->wq, &info->work); return 0; } @@ -453,7 +453,7 @@ void shpchp_queue_pushbutton_work(struct work_struct *work) kfree(info); goto out; } - queue_work(shpchp_wq, &info->work); + queue_work(p_slot->wq, &info->work); out: mutex_unlock(&p_slot->lock); } @@ -501,7 +501,7 @@ static void handle_button_press_event(struct slot *p_slot) p_slot->hpc_ops->green_led_blink(p_slot); p_slot->hpc_ops->set_attention_status(p_slot, 0); - queue_delayed_work(shpchp_wq, &p_slot->work, 5*HZ); + queue_delayed_work(p_slot->wq, &p_slot->work, 5*HZ); break; case BLINKINGOFF_STATE: case BLINKINGON_STATE: -- cgit v1.2.3-55-g7522