panic: sleeping thread & bufwrite: buffer is not busy???

Robert Watson rwatson at
Fri Dec 12 10:38:57 UTC 2008

On Fri, 12 Dec 2008, Kostik Belousov wrote:

>> Unfortunately I cannot provide more debug information at this time
>> because kernel was built without debugging options. (I will rebuild it
>> if needed) However I can still provide some info:
>> - kernel panic while loading modules, just after loding ZFS module (I
>> have RAIDZ configuration) and after a couple of minutes without any
>> visible action on the screen.
>> - I have this panic with *every* build I made after 7 Dec 2008, but I
>> don't remember wchich day exactly I have experienced that for the first
>> time.
>> - For now I'm using kernel builded 7 Dec 2008 and no panic seen at all.
> You are mixing the issues without a reason. To claim that you problem is 
> similar, you need to show the similar backtrace. The panic shown is the late 
> manifestation of a problem, it is kind a catch-all for some sort of locking 
> issues.

This is the second report of weird rwlock-related panics in a week.  We should 
read the code on this one closely, but I can't help but notice that it's 
similar to Roman's report of an rwlock-related panic.  Was there a 
locking/scheduling change in the last week or two in -current that could 
explain these symptoms?

Robert N M Watson
Computer Laboratory
University of Cambridge

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