locking in a device driver (was: use of bus_dmamap_sync)
dinesh at alphaque.com
Thu Oct 27 04:24:55 PDT 2005
carrying on this discussion, what would be a good locking mechanism to use
to protect tsleep() and other sensitive areas in a driver in freebsd 4.x ?
the current code for the driver in 5.x uses mtx_lock and mtx_unlock with
some parts even being protected by mtx_lock(&Giant).
would the use of simple_lock() or s_lock() do, given that SIMPLELOCK_DEBUG
was defined in the 4.x kernel ?
the mechanism is actually a pseudo device driver which communicates with
the real device driver. the pseudo device driver creates a bunch of /dev/
devices which the userland reads/writes to, and the pseudo device driver
then places data in a few buffers.
the real device driver then reads these buffers and uses busdma to send the
data to the device. reading is done by using busdma to read from the device
and then placing the data in these buffers for the pseudo device to return
to the userland process.
locking in the real device driver uses splhigh/splx, but what locking
should be used in the pseudo device driver ?
Regards, /\_/\ "All dogs go to heaven."
dinesh at alphaque.com (0 0) http://www.alphaque.com/
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