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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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