Re: 2.4.21 IDE and IEEE1394+SBP2 regressions, orinoco_pci progress

[Zygo Blaxell]

On Tue, 08 Jul 2003 23:13:08 -0400, jiho wrote:
> Zygo Blaxell wrote:
> Excuse my ignorance -- I suppose I'm blundering around here with a
> number of IDE issues -- but what do you mean by, "at suspend time"?

At the time I either hit the appropriate key sequence on the laptop, or
run the 'apm -s' command, or when battery power drops below an arbitrary
threshold, which causes the laptop to go into a low power mode (memory is
powered, but CPU is stopped and all non-memory-related hardware is turned
off).

> How can there be a "suspend time" while a disk I/O request is "in
> progress"?

For this to happen there has to be a process or processes doing a lot of
disk I/O at the moment that the suspend event occurs (which is typical if
e.g. compiling a kernel while on battery power, and the battery power runs
out half way through).

I'm guessing here, but I suspect that at least one IDE request has been
sent to the drive, but a reply has not been received yet, when the APM
BIOS stops executing Linux and cuts power to the drive.  When the laptop
resumes some time later, the APM BIOS turns the drive back on and resumes
executing Linux.  AFAICT APM expects the OS to take care of re-issuing the
last command to the IDE disk, or expects the OS to avoid issuing a command
just before the OS tells APM that it's ready to suspend.  Either approach
would work.

Linux is still waiting for this command to complete after it resumes, but
of course the drive and controller hardware don't remember what the
command was as they've been turned off in the meantime.

In 2.4.20 and earlier, the kernel would wait a few seconds, then reset the
IDE hardware and try the command again.  In 2.4.21, the kernel locks up
hard.  Judging from my boolean CPU meter (aka the laptop fan, which
activates during periods of high CPU activity), the CPU isn't very busy
when it is locked up like this.