From: David Brownell <[EMAIL PROTECTED]> Date: Wed, 02 Apr 2003 07:52:05 -0800
I got a report of a problem with a high speed CD-ROM that could be reproduced by a simple loop:
dd if=/dev/scd0 of=cdrom.iso cmp /dev/scd0 cdrom.iso
The failure was reported on 2.4, so I wanted to know if it showed up on 2.5 too. (Since usb-storage on 2.5 seems to be more robust.) So I tried it, and it ran fine ... for about an hour, then the script wedged completely.
I thought Arjan and I plugged all such occurences, and I saw Greg's BK changeset with it.
Hmm, interesting -- I couldn't quite tell what that changeset was supposed to do. Seems you're implying that 2.5 still needs similar cleanups (or might).
I could imagine those fixes resolving this, since the report was against 2.4.21-pre6 ... which I think missed those storage fixes. (HC: This suggests that you might want to test against Greg's latest bitkeeper tree, which certainly has those storage fixes.)
And in any case it's not clear to me yet if this particular 2.5 failure relates to any 2.4 failure. I've yet to repeat that test against 2.4.Greg's-latest.
Alt-SysRq-T showed the "dd" blocking in the read; the relevant bits are appended. Disassembly shows that blk_run_queues+0x146 is a CLI instruction right after q->unplug_fn(q).
Yeah, that's what I fixed (with ohci).
Ah -- there we go. I didn't know that's the kind of thing that your patch was trying to fix.
I don't think the EHCI code was doing those particular kinds of things, but now I know what's relevant I may be able to find a similarity. At least on 2.5 I don't yet have a reason to suspect the EHCI code in this case. (And 2.4 EHCI is almost identical...)
Thanks Pete, that's a help.
- Dave
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