Date: Sun, 12 Jul 1998 00:52:51 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: dg@root.com Cc: tlambert@primenet.com, current@FreeBSD.ORG Subject: Re: Arrgh ! resubscribing again again again.... Message-ID: <199807120052.RAA15975@usr08.primenet.com> In-Reply-To: <199807111110.EAA15688@implode.root.com> from "David Greenman" at Jul 11, 98 04:10:56 am
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> >When no backing pages exist (becaues you've used them all up and are > >out of swap space), the process requesting the page as a result of > >the copy on write fault can not have its request satisfied. > > > >The result of an unsatified fault request is a SIGSEGV, or signal 11; > > Wrong. The result of running out of swap space is a SIGKILL, or signal 9. > The bug that people are refering to seems to have been introduced around the > time that John was messing with the VM map code, but might predate that to > when he was messing with some of the swap pager algorithms. Hmmm. I was able to cause the problem (with SIGSEGV) by mapping a large shared memory segment, and then traversing the pages to dirty them (one byte per page). I see in the VM code where a SIGKILL could result, but it seems to me that the page table entry exists, it just doesn't have pages to back it, and when the page to back the entry fails allocation, you get SIGSEGV, since it isn't mapped when you do the reference. Am I reading this code wrong? Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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