The reason the drivers drop their locks is
that the network stack frequently holds locks over calls to driver output
routines. As a result, driver locks tend to follow network stack locks in the
lock order--at least, for drivers that have a single lock covering both send
and receive paths (quite common). As a result, the driver must drop the
driver lock before calling into the stack to avoid a lock order reversal.
Just to further clarify the corollary to this statement - drivers that
separately lock their softc, tx, and rx queues don't need to drop the
lock across if_input as there is no possibility of lock order reversal
between the input and the output path.
-Kip
_______________________________________________
freebsd-net@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "[EMAIL PROTECTED]"
