On 26-Mar-2002 Alfred Perlstein wrote:
> * Alfred Perlstein <[EMAIL PROTECTED]> [020326 14:43] wrote:
>> * Kris Kennaway <[EMAIL PROTECTED]> [020324 14:26] wrote:
>> > The bento cluster is now running with WITNESS enabled to try and track
>> > down some odd UMA lock corruption panics.  Instead, it found the
>> > following lock order reversal in sys_pipe.c overnight:
>> > 
>> > Mar 24 09:02:29 <user.crit> gohan13 kernel: lock order reversal
>> > Mar 24 09:02:29 <user.crit> gohan13 kernel: 1st 0xd99d6500 pipe mutex @
>> > /local0/scratch/usr/src/sys/kern/sys_pipe.c:450
>> > Mar 24 09:02:29 <user.crit> gohan13 kernel: 2nd 0xd971cddc process lock @
>> > /local0/scratch/usr/src/sys/kern/kern_sig.c:2093
>> > 
>> > Those source references are from a -current kernel from last night.
>> Are you %100 on that?  How did you get this to happen?
>> I can see where I hold the pipe lock, then try to get a proc lock,
>> but not the other way around...
>> Any ideas?
> Note that I can pretty trivially fix this by dropping the pipe lock
> while calling pgsigio in pipeselwakeup(), however I will then have to
> make sure the callers of pipeselwakeup() can deal with someone else
> mucking with the pipe during the call.
> Anyhow, wtf doesn't witness print out at least one instance of the
> old locking?  Basically let me know where locking is happening in
> the other direction?

That's easy to achieve.  Add a static lock ordering in the compiled in arrays,
then it will let you know when you do the other way.  It may be an indirect
relationship and not a direct one as well.  The allproc/filedesc thing was an
instance of indirect relationships determining the order.


John Baldwin <[EMAIL PROTECTED]>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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