Messages in this thread | | | Subject | [block subsystem] Need help to prevent races on unexpected device removal | From | Maxim Levitsky <> | Date | Sun, 03 Jan 2010 21:13:47 +0200 |
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During development of hotplug support for mtd translation layer I seems to be unable to figure a way to prevent following race:
First of all, a block device is registered. I attach a private structure to that device to save all internal information.
Then out of the blue (when user pulls off the card) I receive a request to remove the device.
In the function that handles such removal, I do:
del_gendisk(... blk_start_queue
stop thread that processes the requests
blk_cleanup_queue(old->rq);
The problem is that I don't know where/when to free the private structure.
I though about adding a field to the structure, with name 'invalid', so that release will not attempt to go futher, but free the structure, but what happens if release is never called? In other words this will work as long as there is a user of the block device.
I thought then that I can detect that condition and free the structure in the removal function itself, but then I get a race with ->open running in same time, and mutex will not prevent it, I will have to release it somwhen, and then ->open will access a freed structure....
Best regards, Maxim Levitsky
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