Re: pciehp resume handler - racy?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Alan Jenkins wrote:
Hi,

I've been hacking on the PCI hotplug driver otherwise known as
eeepc-laptop.  At one point I reliably triggered a race on resume.  In
the hot-unplug case, it seemed that the resume handler would try to
remove the PCI device at the same time as an acpi notification (run in a
workqueue) tried to do the same thing.  The result was an OOPS.  My
conclusion is that the PCI hotplug core does not protect against
multiple simultaneous removals of the same device.

Though I don't know hotplug driver for eeepc-laptop at all, I guess
it doesn't use pci_hp_register(), which is for registering a hotplug
slot to pci hotplug core. The pci_hp_register() prevents a hot-plug
slot from being managed by multiple hotplug controller drivers at
the same time. Using pci_hp_register() would be one of the solution
for eeepc-laptop hotplug driver.


pciehp appears to have an analogous problem.  Assuming pciehp_force is
set, the resume handler can hot-unplug the device.  The interrupt
handler could try to hot-unplug the device at the same time.  Should the
resume handler take the slot mutex to avoid this problem?


Hot-plug operations for the same hotplug slot are serialized by
crit_sect mutex of struct controller in pciehp_enable_slot() and
pciehp_disable_slot(). So I don't think multiple hot-plug
operations for the same slot would be executed at the same time.

Thanks,
Kenji Kaneshige


diff --faked-up a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -382,15 +382,18 @@ static int pciehp_resume (struct pcie_device *dev)
 		/* reinitialize the chipset's event detection logic */
 		pcie_enable_notification(ctrl);
t_slot = pciehp_find_slot(ctrl, ctrl->slot_device_offset);
+		mutex_lock(&t_slot->lock);
/* Check if slot is occupied */
 		t_slot->hpc_ops->get_adapter_status(t_slot, &status);
 		if (status)
 			pciehp_enable_slot(t_slot);
 		else
 			pciehp_disable_slot(t_slot);
+
+		mutex_unlock(&t_slot->lock);
 	}
 	return 0;
 }
 #endif /* PM */


Regards
Alan

--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [DMA Engine]     [Linux Coverity]     [Linux USB]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Greybus]

  Powered by Linux