Messages in this thread |  | | Date | 9 Feb 2013 02:05:58 -0500 | From | "George Spelvin" <> | Subject | Re: [PATCH 0/7] 3.8-rc regression with pps-ldisc due to 70ece7a731 |
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As a followup, testing my fixes has revealed an old bug in the PPS driver that I'm trying to figure out how to solve.
Basically, pps_unregister_cdev does
device_destroy(pps_class, pps->dev->devt); cdev_del(&pps->cdev);
And device_destroy ends up calling pps->dev->release, which is pps_device_destruct, which does
mutex_lock(&pps_idr_lock); idr_remove(&pps_idr, pps->id); mutex_unlock(&pps_idr_lock);
kfree(dev); kfree(pps);
Now the problem is that the kfree(pps) happens *before* the cdev_del(&pps->cdev) call, which is Not Good.
I'm trying to figure out The Right Thing to do in this case and include a fix for that, too. It's not a regression, but it is a fairly serious bug.
Advice gratefully received, but I'll figure it out on my own, if not. The most obvious kludge is to wrap the pps_unregister_cdev operations in device_get/device_put, to force the release callback to be delayed until later.
I'm hoping for something prettier, though. The other option I'm thinking about is to move one or both deallocations to the (currently stub) pps_cdev_release function.
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