[lkml]   [2005]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: User mode drivers: part 1, interrupt handling (patch for 2.6.11)
    >>>>> "Jon" == Jon Smirl <> 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.

    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 peterc AT
    The technical we do immediately, the political takes *forever*
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 14:11    [W:0.020 / U:3.764 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site