Re: [bug report] NFS and uninterruptable wait states

[Doug McNaught <doug@wireboard.com>]

Phillip Susi <psusi@cfl.rr.com> writes:

> The other day I was trying to set up an NFS mount to my room mate's system, 
> and ran into what I at least, call a bug.  When I tried to mount his NFS 
> export, the mount command locked up, and would not die.  Not even a SIGKILL 
> would do any good.  According to ps, the mount process was in the 'D' - 
> uninterruptable wait state.  It also looked like the WCHAN was rpc_ 
> something.  I think it was waiting for an rpc call to return in the D state, 
> and it never did return.  The bug here is that it should NOT be waiting in 
> the D state for something that could never happen.  For that matter, why 
> should anything ever need to wait in an uninterruptable state?  Whenever you 
> wait, you should expect the possibility of being interrupted, check for that 
> when you wake up, and if you were, clean up and return so the signal can be 
> processed.

NFS does this (wait in D state) by default in order to prevent naive
applications from getting timeout errors that they're not equipped to
handle--the idea being that, if an NFS server goes down, programs
using it will simply freeze and recover once it returns, rather than
getting a timeout error and possibly becoming confused.

If you don't like this behavior, mount with 'soft' and/or 'intr'
options--see the manpage.

-Doug
-- 
Free Dmitry Sklyarov! 
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