Matt,

> > This is an older Heartbeat haresources-based cluster. Would your 
> > suggestion work even when kill -9 won't kill the nfs, nfsd, or
> > mfsd4 processes? They simply would not die. I suspect this 
> is because 
> > they are in use by another process.
> 
> If so, then kill *that* process.  lsof and/or fuser can help 
> a lot with determining what's using things and killing those things.
> 

Couldn't it be someone sitting in the mounted directory on an NFS client
computer? Getting to that might be hard. Is there some way to get a hung
nfsd to quit waiting for whatever it is waiting for?

> 
> Under Linux, a process in state D (waiting for a syscall to 
> return) *cannot* be killed, even with SIGKILL.  The kernel 
> programmers found a number of circumstances where terminating 
> a process in state D could lead to Undefined Behavior, as I 
> understand it.  The example I remember was a process doing a
> read() syscall on a dodgy disk.  Kernel code says, "When the 
> read from the disk completes, I'll use DMA to shove the 
> result into page 0x131072."  Disk can't deliver immediately 
> because it's flaky.  User kill -9s the process. 
> Kernel MM code releases page 0x131072, some other process 
> grabs hold of that page.  Disk eventually gets its act 
> together, uses DMA to write data to that page, other process 
> gets its data corrupted.  How embarrassing.
> 

Thanks for the explanation. I figured it was something like that. It's
way too frustrating a problem for someone not to have fixed it
otherwise.

--Eric







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