:I'm getting these on NFS for loopback.
Can you verify that it's the same as Poul's by breaking into DDB
and doing a trace ?
I have very little time, but what I think may be going on is that
current may be exposing a bug in the specfs fsync code related to
flushing dirty buffers which already have a background bitmap write
I think what is going on is that interrupt threads are not able to
run in -current, whereas interrupts do run in -stable, and an interrupt
completing the write on a buffer is what breaks us out of the
infinite loop. I noticed in Poul's 'ps' output that a number of
interrupt threads were runnable, but not getting any cpu to run.
The way to test this hypothesis is to give up the cpu for a tick in the
specfs fsync loop, allowing interrupt threads to run. Maybe do a
tsleep for hz/10 every 500 iterations or something like that.
If this fixes the problem, then we have confirmation.
Alternatively someone can work up a simple MARK/SCAN for specfs's fsync,
ala what we do in FFS's fsync, and try that. I think MARK/SCAN may
be the ultimate solution but we should home in on the problem before
tring it out.
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