On Thu, Apr 07, 2011 at 11:01:02AM -0400, Alan Stern wrote: > On Thu, 7 Apr 2011, Roedel, Joerg wrote: > > > So we could access the data structure without any locks if we want using > > atomic_t for the probe_count and isoc_reqs members. But as I've seen > > meanwhile the lock still needs to protect the access to the hardware in > > the usb_amd_quirk_pll() function. > > So its probably not worth the work, what do you think? > > You might as well use the spinlock. Yes, since we need it anyway for protecting the hardware-access we can leave everything as is (with the fix). > However, is there a good reason to zero out the amd_chipset members in > usb_amd_dev_put()? Can these things be added and removed dynamically? > If they can't then the data should remain valid indefinitely once it > has been probed, and you could call pci_dev_put() at the end of > usb_amd_find_chipset_info(). Well, in a real system it is indeed very unlikely that the chipset is hotplugged. But for formal correctness it is right to hold a reference to the pci_dev struct as long as we rely on a pointer to it. > And if they can, is it valid to call pci_dev_put() in usb_amd_dev_put() > while holding a spinlock? You might want to move those calls to the > end of the function. I just had a look, pci_dev_put seems to be invalid in atomic context too. If the reference count drops to 0 (which is very unlikely for the chipset devices) the device and its kobject are released. This causes a uevent to be sent to userspace which does GFP_KERNEL allocations and all the stuff. So for formal correctness the pci_dev_put calls need to be moved out of the spinlock too. Regards, Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
