Messages in this thread |  | | | Date | Thu, 7 Mar 2002 01:13:11 -0800 (PST) | | From | Andy Tai <> | | Subject | "layered" block devices and deadlock problems |
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Hi, I have been trying to write a kernel driver for a "layered" block device, that is, a virtual device which sits on top of actual physical devices and redirects read/write requests to them. To avoid problems in the interrupt context I save the requests in a queue in the request function and have a kernel thread pulling the requests out of the queue and then in turn calling read() or write() functions of the physical block device.
However, I keep running into deadlocks. Sometimes the kernel thread will hang on waiting for free request structures. Other times it will hang in wait_for_buffer() in buffer.c. In both cases the system won't respond to any new shell commands I typed in. (But existing processes like xosview and top continue to run) Since I am not familiar with the internal workings of the buffer cache, can anyone give me hints on how to avoid deadlocks in layered drivers? Or pointers to useful documentation for this kind of tasks are also appreciated.
Thanks.
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