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Date: Sun, 26 Oct 2003 15:34:05 -0500 (EST)
From: Jeff Roberson <jroberson@chesapeake.net>
To: Alan Cox <alc@cs.rice.edu>
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cc: Alan Cox <alc@FreeBSD.org>
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Subject: Re: cvs commit: src/sys/vm swap_pager.c
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On Sun, 26 Oct 2003, Alan Cox wrote:

> With this change, you may see:
>
> lock order reversal
>  1st 0xc24aab90 vm object (vm object) @ vm/swap_pager.c:1319
>  2nd 0xc070f180 swap_pager swhash (swap_pager swhash) @ vm/swap_pager.c:1832
>  3rd 0xc1036b90 vm object (vm object) @ vm/uma_core.c:876
>
> This is also a false positive.  The only vm object that is locked
> after acquiring the "swap_pager swhash" mutex is one used internally
> in UMA.  We will never acquire this vm object's mutex followed by
> the "swap_pager swhash" mutex.

Does the swap_zone really need a backing object?  This is just so the
operation wont fail for lack of kva, right?  Is this really necessary
here?  I thought we did it before so that we could allocate at interrupt
time, since pages could be allocated, but kva could not.  I doubt this
code runs at real interrupt time anymore.


>
> Regards,
> Alan
>
> On Sun, Oct 26, 2003 at 11:55:35AM -0800, Alan Cox wrote:
> > alc         2003/10/26 11:55:35 PST
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/vm               swap_pager.c
> >   Log:
> >    - Introduce and use a mutex synchronizing access to the swblock hash table.
> >
> >   Revision  Changes    Path
> >   1.234     +20 -4     src/sys/vm/swap_pager.c
>