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<tj@xxxxxxxxxx> --- 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 <jgarzik@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
