Tejun Heo wrote:
Hello, all.
This has been going on for quite some time now but I finally succeeded
to reproduce the problem and find out what has been going on. It
wasn't drive's or controller's fault. The spurious completion
detection logic was wrong which makes all of this my fault. :-)
The attached patch induces NCQ spurious completions by inserting
artificial delays during irq handling. The following is log with the
patch applied.
A [ 1125.478813] ata35: MON issue=0x0 SAct=0x1 sactive=0x3 SDB
FIS=004040a1:00000002
B [ 1125.480248] ata35: MON issue=0x4 SAct=0x6 sactive=0x7 SDB
FIS=004040a1:00000001
C [ 1125.481614] ata35: MON issue=0x0 SAct=0x5 sactive=0x7 SDB
FIS=004040a1:00000002
D [ 1125.481704] ata35: YYY 0x2 -> 0x4
E [ 1125.481722] ata35: XXX issue=0x0 SAct=0x1 sactive=0x1 SDB
FIS=004040a1:00000004
F [ 1125.483087] ata35: MON issue=0x0 SAct=0x0 sactive=0x1 SDB
FIS=004040a1:00000001
G [ 1125.484297] ata35: MON issue=0x4 SAct=0x6 sactive=0x7 SDB
FIS=004040a1:00000001
Thanks a lot for tracking this down, and thanks even more for being
humble enough to admit mistakes. More kernel hackers should follow your
example.
I continue to be a proud mentor, watching you kick ass on the Linux
kernel scene :)
Jeff
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