ATA + DMA still giving repeatable freezes

[Kirk Strauser]

At 2003-12-20T00:17:00Z, Robert Watson <rwatson at FreeBSD.org> writes:

> FYI, I had this problem on a notebook and foudn that disabling "device
> apic" made things clear up.  Try it and see if it helps, and if it does,
> post as much.  I'm busy testing to make sure my observation is right on my
> system.  I also saw fairly frequent hangs starting or leaving XWindows,
> and John Baldwin hypothesized there was an interaction between DRM and the
> interrupt code.

Robert, I wanted to get in some more testing before reporting back.  I
cvsup'ed again and built world and kernel.  This time, I started with plain
GENERIC and made minor changes until I could reproduce the hangs.
Basically, commenting out "options WITNESS" and "options WITNESS_SKIPSPIN"
was enough to trigger the problem; I'm guessing that these options slow down
the system enough that timing issues disappear.

After adding this to my /boot/loader.conf.local:

    hw.ata.ata_dma="0"
    hint.acpi.0.disabled="1"

I no longer get system hangs, although I do get these messages at random
intervals during heavy ATA IO:

    ad0: TIMEOUT - READ_MUL retrying (2 retries left)
    ata0: resetting devices ..
    done

-- 
Kirk Strauser
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