Date: Sat, 4 Jun 2016 15:11:21 -0400 From: Michael Butler <imb@protected-networks.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Matthew Macy <mmacy@nextbsd.org>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org>, alc@freebsd.org Subject: Re: repeatable panic on pageout with 945GM Message-ID: <b69a8693-9fa8-12d8-d09d-d0291881bb80@protected-networks.net> In-Reply-To: <20160604190237.GD38613@kib.kiev.ua> References: <2490f1c7-8153-ece3-49ed-4b3886564fd7@protected-networks.net> <da19738b-6bf1-10a3-4428-43b6095ec35a@protected-networks.net> <205d4423-b834-9a21-785f-fa15d44c78ec@protected-networks.net> <CAHM0Q_PR5Aoak6A7f=tsRy0DJFCmLDVfRGpceZ0mXU3P%2BxO8DA@mail.gmail.com> <1551419a1db.12929035f45012.326107747932338888@nextbsd.org> <939f9d2b-e925-e8e0-0ff3-8d90623728c6@protected-networks.net> <1551c5dbd86.c68532b5123717.566503881838650848@nextbsd.org> <20160604174745.GB38613@kib.kiev.ua> <88ad4228-2583-8a91-1751-d16f7a51de91@protected-networks.net> <20160604190237.GD38613@kib.kiev.ua>
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On 06/04/16 15:02, Konstantin Belousov wrote: > On Sat, Jun 04, 2016 at 02:59:01PM -0400, Michael Butler wrote: >> On 06/04/16 13:47, Konstantin Belousov wrote: >> >> [ .. snip .. ] >> >>> I believe that this is a bug in amd64 pmap. Fictitious pages are not >>> promoted, in particular, the pv_table array does not span over the >>> dynamically registered fictitious ranges. As result, pa_to_pvh() returns >>> garbage and pvh must not be accessed in the case of 'small_mappings' in >>> several pmap functions. It is typically not accessed, except in case >>> when we have to drop and reacquire pv lock, to avoid LOR with pmap. >>> >>> i386 does not have the issue, due to pvh_global_lock. >>> >>> Below is the supposed fix (not tested). >> >> [ .. snip .. ] >> >> Is this something I should test and, should it not introduce any other >> issues, might get committed? > > Would be nice to test. I expect that this patch is going to be committed, > after the review. > I will do so this evening and add a kprintf to the previous band-aid to see if it prevents the problematic condition from occurring. If it counts, my test laptop has a Core-2 Duo so it is entirely possible that multiple threads are running concurrently, imb
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