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    SubjectRe: [PATCH 11/12] libata: use IRQ expecting
    On 06/13/2010 11:31 AM, Tejun Heo wrote:
    > Thanks to its age, ATA is very susceptible to IRQ delivery problems in
    > both directions - lost and spurious interrupts. In traditional PATA,
    > the IRQ line is ultimately out of the controller and driver's control.
    > Even relatively new SATA isn't free from these issues. Many
    > controllers still emulate the traditional IDE interface which doesn't
    > have reliable way to indicate interrupt pending state and there also
    > is an issue regarding the interpretation of nIEN on both sides of the
    > cable.
    >
    > Most of these problems can be worked around by using the new IRQ
    > expecting mechanism without adding noticeable overhead. In ATA,
    > almost all operations are initiated by the host and the controller
    > signals progress or completion using IRQ. IRQ expecting can easily be
    > added in libata core and applied to all libata drivers.
    >
    > Signed-off-by: Tejun Heo<tj@kernel.org>
    > ---
    > drivers/ata/libata-core.c | 15 +++++++++++++--
    > drivers/ata/libata-eh.c | 4 +++-
    > drivers/ata/libata-sff.c | 37 +++++++++++++++++++------------------
    > include/linux/libata.h | 2 ++
    > 4 files changed, 37 insertions(+), 21 deletions(-)
    >
    > diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
    > index ddf8e48..9a0aaa0 100644
    > --- a/drivers/ata/libata-core.c
    > +++ b/drivers/ata/libata-core.c
    > @@ -4972,6 +4972,8 @@ void ata_qc_complete(struct ata_queued_cmd *qc)
    > {
    > struct ata_port *ap = qc->ap;
    >
    > + unexpect_irq(ap->irq_expect, false);
    > +
    > /* XXX: New EH and old EH use different mechanisms to
    > * synchronize EH with regular execution path.
    > *

    Unconditional use of unexpect_irq() here seems incorrect for some cases,
    such as sata_mv's use, where ata_qc_complete() is called multiple times
    rather than a singleton ata_qc_complete_multiple() call.

    Jeff








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