Date: Sun, 26 Oct 2003 14:44:55 -0600 From: Alan Cox <alc@cs.rice.edu> To: Jeff Roberson <jroberson@chesapeake.net> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/vm swap_pager.c Message-ID: <20031026204455.GC20658@cs.rice.edu> In-Reply-To: <20031026153051.X43805-100000@mail.chesapeake.net> References: <20031026201944.GA20658@cs.rice.edu> <20031026153051.X43805-100000@mail.chesapeake.net>
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On Sun, Oct 26, 2003 at 03:34:05PM -0500, Jeff Roberson wrote: > 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. > What would you propose? I believe switching to page_alloc() would also produce a false LOR warning. Regards, Alan > > > > > 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 > >
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