Comment 22 for bug 397096

Tormod.
I'll try your tip and see what happens.
In the meantime I can add some observations: Alongside with the freeze entry in the log there are allways these entries for me:

[ 159.816518] ata1: drained 134 bytes to clear DRQ.
[ 159.816557] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[ 159.816586] ata1.00: cmd c8/00:30:67:5c:d4/00:00:00:00:00/e6 tag 0 dma 24576 in
[ 159.816591] res 40/00:ff:00:00:00/00:00:00:00:00/40 Emask 0x4 (timeout)
[ 159.816601] ata1.00: status: { DRDY }
[ 159.872074] ata1: soft resetting link
[ 160.054175] ata1.00: configured for UDMA/100
[ 160.054189] ata1.00: device reported invalid CHS sector 0
[ 160.054210] ata1: EH complete

Theese entries are allways associated with a lit HD LED and the system is frozen for a while. Sometimes the file system gets remounted ro after having been corrupted.

Sometimes the system decides that the hard drive is only capable of UDMA/66 and changes it to that after the soft reset.

The line: "device reported invalid CHS sector 0", seems to be an "off by one error" reported in http://patchwork.kernel.org/patch/41773/ and fixed upstream, and not seen often "The bug isn't very visible because ata_tf_read_block() is used only when generating sense data for a failed RW command and CHS addressing isn't used too often these days.", Tejun Heo says.

But why does the hard drive need to be "soft reset"?

I never had theese problems with Jaunty, or earlier releases that I have upgraded from.