linux-kernel - Intel IOMMU double lock

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Date:	Mon, 14 Jun 2010 17:17:32 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	David Woodhouse <dwmw2@...radead.org>
CC:	iommu@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Intel IOMMU double lock

Hi,

stanse found the following double lock.

In get_domain_for_dev:
  spin_lock_irqsave(&device_domain_lock, flags);
  domain_exit(domain);
    domain_remove_dev_info(domain);
      spin_lock_irqsave(&device_domain_lock, flags);
      spin_unlock_irqrestore(&device_domain_lock, flags);
  spin_unlock_irqrestore(&device_domain_lock, flags);

I don't know how to solve this properly. Is this OK:
diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 796828f..e6ac8e7 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -1874,14 +1874,15 @@ static struct dmar_domain
*get_domain_for_dev(struct pci_dev *pdev, int gaw)
                        }
                }
                if (found) {
+                       spin_unlock_irqrestore(&device_domain_lock, flags);
                        free_devinfo_mem(info);
                        domain_exit(domain);
                        domain = found;
                } else {
                        list_add(&info->link, &domain->devices);
                        list_add(&info->global, &device_domain_list);
+                       spin_unlock_irqrestore(&device_domain_lock, flags);
                }
-               spin_unlock_irqrestore(&device_domain_lock, flags);
        }

 found_domain:

thanks,
-- 
js
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