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DragonFly kernel List (threaded) for 2006-08
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Re: Working on vnode sequencing and locking - HEAD will destabilize for a little bit

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 10 Aug 2006 09:57:39 -0700 (PDT)

:On 2006-08-09, Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> wrote:
:>     And, poof, no more indefinite blocking states in the kernel for NFS or
:>     for the upcoming userland VFS or clustering.
:>     There will be fine-grained range locks to maintain UNIX atomicy
:>     requirements, but since they aren't going to be hard locks they won't
:>     prevent basic things like ^C from working properly.
:Btw, what does "^C working properly" mean? AFAIK SUS says/implies that
:filesystem related syscalls shouldn't be interruptible, with the
:exception of read and write.

    Well, maybe not ^C so much as SIGKILL (signal 9).  The reality is that
    the requirement never took into account things like NFS or really any
    remote filesystem.  This is why NFS has a shim called the 'intr' option
    that allows you to ^C a filesystem op blocked in an NFS RPC.

    I think a distinction has to be made between normal signal interruption,
    which we clearly do not want to allow, and termination cases which
    we clearly do want to allow.

					Matthew Dillon 

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