Date: Thu, 4 Mar 2004 18:55:24 -0800 From: Marcel Moolenaar <marcel@xcllnt.net> To: Nate Lawson <nate@root.org> Cc: current@freebsd.org Subject: Re: bug in vm_contig.c? [was: Re: ACPI crash with recent changes] Message-ID: <20040305025524.GA601@dhcp01.pn.xcllnt.net> In-Reply-To: <20040304161108.U26303@root.org> References: <20040304025223.GA622@dhcp01.pn.xcllnt.net> <20040304161108.U26303@root.org>
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On Thu, Mar 04, 2004 at 04:16:20PM -0800, Nate Lawson wrote: > Try reverting these two changes. This is not an ACPI problem. The fact > that ACPI needs to allocate some memory early on in the boot for its sleep > code is what triggers this bug. > > src/sys/vm/vm_contig.c:1.31 > src/sys/vm/vm_page.c:1.277 > > http://docs.freebsd.org/cgi/getmsg.cgi?fetch=326708+0+current/cvs-src > > I think the bug is the loop accessing i - 1 right from the start. It may > be correct to do: for (i = start + 1; ... > But I don't know this section of the code. Yes, start can be and is 0 at that moment. Hence, i can be 0 and i - 1 can be fatal. Initializing the loop with start + 1 fixes the problem. To be precise, we're talking about: Index: vm_contig.c =================================================================== RCS file: /home/ncvs/src/sys/vm/vm_contig.c,v retrieving revision 1.31 diff -u -r1.31 vm_contig.c --- vm_contig.c 2 Mar 2004 08:25:58 -0000 1.31 +++ vm_contig.c 5 Mar 2004 02:41:38 -0000 @@ -230,7 +230,7 @@ } } mtx_lock_spin(&vm_page_queue_free_mtx); - for (i = start; i < (start + size / PAGE_SIZE); i++) { + for (i = start + 1; i < (start + size / PAGE_SIZE); i++) { pqtype = pga[i].queue - pga[i].pc; if ((VM_PAGE_TO_PHYS(&pga[i]) != (VM_PAGE_TO_PHYS(&pga[i - 1]) + PAGE_SIZE)) || -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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