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SubjectRe: [PATCH 11/12] libata: use IRQ expecting
On 07/02/2010 10:41 AM, Tejun Heo wrote:
> Hello, Jeff.
> So, something like the following. This should be applied on top of
> the two previous libata patches. The amount of code in the hot path
> is very small. Compared to the cpu actually taking an interrupt and
> accessing hardware, it should be negligible, and this will give us
> working and acceptably performing systems in the presence of most
> types of IRQ problems.
> Thanks.
> Subject: [PATCH] libata: use IRQ expecting
> Legacy 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 controllers share this problem as many 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.
> Controllers with native interface have fewer problems compared to the
> ones which use SFF but they still are affected by IRQ misrouting or
> broken MSI implementations.
> IRQ delivery problems on ATA are particularly nasty because it
> commonly hosts installation and/or booting.
> Most of these problems can be worked around by using the new IRQ
> expecting mechanism without adding any 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<>
> ---
> drivers/ata/libata-core.c | 55 ++++++++++++++++++++++++++++++----------------
> drivers/ata/libata-eh.c | 4 ++-
> drivers/ata/libata-sff.c | 37 +++++++++++++++---------------
> include/linux/libata.h | 2 +
> 4 files changed, 60 insertions(+), 38 deletions(-)

I suppose the few cycles it costs are worth it...

Assuming this new version (from July 2) is tested,

Acked-by: Jeff Garzik <>

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