On Mon, 14 Mar 2005 12:42:27 +1100, Peter Chubb <[EMAIL PROTECTED]> wrote: > >>>>> "Jon" == Jon Smirl <[EMAIL PROTECTED]> writes: > > >> The scenario I'm thinking about with these patches are things like > >> low-latency user-level networking between nodes in a cluster, where > >> for good performance even with a kernel driver you don't want to > >> share your interrupt line with anything else. > > Jon> The code needs to refuse to install if the IRQ line is shared. > > It does. The request_irq() call explicitly does not include SA_SHARED > in its flags, so if the line is shared, it'll return an error to user > space when the driver tries to open the file representing the interrupt.
Please put some big comments warning people about adding SA_SHARED. I can easily see someone thinking that they are fixing a bug by adding it. I'd probably even write a paragraph about what will happen if SA_SHARED is added. > > Jon> Also what about SMP, if you shut the IRQ off on one CPU isn't it > Jon> still enabled on all of the others? > > Nope. disable_irq_nosync() talks to the interrupt controller, which > is common to all the processors. The main problem is that it's slow, > because it has to go off-chip. > > -- > Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au > The technical we do immediately, the political takes *forever* > -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
