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| author | Bjorn Helgaas <bhelgaas@google.com> | 2013-01-11 12:21:15 -0700 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2013-01-14 10:23:22 -0700 |
| commit | f652e7d2916fe2fcf9e7d709aa5b7476b431e2dd (patch) | |
| tree | 3de39a91ba274a307e11face7f5bbb8a3f7244b5 /drivers/pci/hotplug/shpchp_ctrl.c | |
| parent | d347e75847c1fb299c97736638f45e6ea39702d4 (diff) | |
| download | blackbird-op-linux-f652e7d2916fe2fcf9e7d709aa5b7476b431e2dd.tar.gz blackbird-op-linux-f652e7d2916fe2fcf9e7d709aa5b7476b431e2dd.zip | |
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 <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org
Diffstat (limited to 'drivers/pci/hotplug/shpchp_ctrl.c')
| -rw-r--r-- | drivers/pci/hotplug/shpchp_ctrl.c | 6 |
1 files changed, 3 insertions, 3 deletions
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: |
