DOC2000 + PPM-TX166 (PATCH)
jduchek at genaero.com
Wed Nov 5 12:20:30 EST 2003
Hello. I'm not subscribed to the mailing list, so please, if you could
make sure any replies for me go to my address and not to the list, I
We saw a problem (actually, a pretty big problem) wherein when a sync()
was done on a filesystem on the DoC we were using, it would hang and
never come back. The system was perfectly responsive, except trying to
talk to the DoC wasn't going to happen again until reboot. The problem
would never occur if we let the fs sync itself -- that is, just wait a
few minutes until the buffers have been cleared.
I traced the problem down to the cond_resched() in WaitReady in
doc2000.c. Removing cond_resched() made the problem go away (and the
system unresponsive while doing any DoC access). Replacing the
udelay(1) and cond_resched() with a yield() fixes everything. The patch
is short and appended to this message. I believe the patch should be
Good for all users, although I'm not sure why we don't see this problem
on some other setups. My best guess is that the other setups we are
using have Geode processors, which I don't believe have a TSC, and our
P-MMX does have one, and udelay() is totally different depending on the
existence of a TSC.
For those curious, we are using an unpatched 2.4.22 kernel on a
WinSystems PPM-TX166. The DoC in question is a 48M Industrial (X) rated
chip. We saw the problem with both msdos and ext2 filesystems.
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