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[Xen-devel] FALSE ALARM Re: Xen crash during boot with debug=y

To: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>

From: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>

Date: Tue, 2 Jun 2009 18:36:14 +0100

Delivery-date: Tue, 02 Jun 2009 10:36:40 -0700

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List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Seems I did the first build with debug=n, and subsequent builds with debug=y (apparently) didn't catch pci.c. Modifying the file at all caused it to be recompiled, which changed the spinkock init code properly. Second afternoon wasted chasing a didn't-make-mrproper bug... -George On Tue, Jun 2, 2009 at 6:19 PM, George Dunlap <George.Dunlap@xxxxxxxxxxxxx> wrote: > Hm, I added some code to the check_lock() to print whenever it was > initializing, and found that the lock in pci.c was initialized to > zero. > > So I added some code to double-check the lock, modifying the layout of > pci.c slightly, and the problem went away. > > Which likely means that there's a buffer overflow somewhere clobbering > the spinlock debug value. Fun, fun, fun... > > -George > > On Tue, Jun 2, 2009 at 4:09 PM, George Dunlap > <George.Dunlap@xxxxxxxxxxxxx> wrote: >> I'm getting the following panic in Xen with tip when building with >> debug=y. It seems to be something with the spinlock/irq >> sanity-checking code; but it doesn't make any sense, because the lock >> in question is defined statically in xen/arch/x86/pci.c, and only used >> two places in that file, with irqsave/irqrestore both times. Any >> ideas? >> >> -George >> >> (XEN) Freed 140kB init memory. >> (XEN) Xen BUG at spinlock.c:24 >> (XEN) ----[ Xen-3.5-unstable x86_64 debug=y Tainted: C ]---- >> (XEN) CPU: 0 >> (XEN) RIP: e008:[<ffff828c8011b7b7>] check_lock+0x3d/0x49 >> (XEN) RFLAGS: 0000000000010046 CONTEXT: hypervisor >> (XEN) rax: 0000000000000000 rbx: ffff828c8020fa68 rcx: 0000000000000001 >> (XEN) rdx: 0000000000000000 rsi: 0000000000000001 rdi: ffff828c8020fa6c >> (XEN) rbp: ffff828c8028fd38 rsp: ffff828c8028fd38 r8: 0000000000000000 >> (XEN) r9: ffff828c8028fee4 r10: 0000000000cfbb00 r11: 000000000000ffff >> (XEN) r12: 0000000000000286 r13: 0000000000000004 r14: 0000000000000000 >> (XEN) r15: 0000000000000000 cr0: 000000008005003b cr4: 00000000000026f0 >> (XEN) cr3: 000000012ffae000 cr2: 00000000c1013fe8 >> (XEN) ds: e021 es: e021 fs: 0000 gs: 0000 ss: 0000 cs: e008 >> (XEN) Xen stack trace from rsp=ffff828c8028fd38: >> (XEN) ffff828c8028fd58 ffff828c8011ba2f 0000000000000004 0000000080000008 >> (XEN) 0000000000000000 ffff828c80161187 0000000000000004 ffff828c8028fdb8 >> (XEN) 0000000000000cfc ffff828c80167ba2 ffff8300cf2fa000 0000000000000000 >> (XEN) 0000000000000cfc ffff828c8028fe88 ffff828c8028ff28 0000000000000000 >> (XEN) ffff828c8028ff18 ffff828c8016b11c ffff83010000f800 ffff8300cf2fa000 >> (XEN) ffff828c8028fe78 ffff828c8015e527 ffff828c8028fe28 0000000000000282 >> (XEN) 0000000000000282 0000000000000286 000000008028fe58 ffff83012ffc6308 >> (XEN) ffff83012feb9a80 0000000000000006 00000000ff750000 ffff8300cf2fa000 >> (XEN) ffff828c8028fe78 ffff828c80162f66 000000000000e021 ffff828402000020 >> (XEN) ffff83012feb9a80 0000000000000006 00000004025fd720 0000000400000004 >> (XEN) 00000000c0603d87 ffff828c8015ebf6 828c801db970b948 c390ed90d1ffffff >> (XEN) 00000000ff750000 000000008011d687 000000012feb9067 ffff83012ffcc0e0 >> (XEN) ffff828c8028ffed 00000000ffffffff 0000000000000000 ffff8300cf2fa000 >> (XEN) 0000000000000000 00c0bb0000000000 0000000000000000 ffff8300cf2fa000 >> (XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >> (XEN) 00007d737fd700b7 ffff828c801db6db 0000000000000000 0000000000000000 >> (XEN) 0000000000000000 0000000000000000 00000000c05f3f34 0000000000000cfc >> (XEN) 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >> (XEN) 0000000000000000 0000000000000000 0000000000000cfc 0000000000000000 >> (XEN) 0000000000000000 0000000d00000000 00000000c0603d86 000000000000e019 >> (XEN) Xen call trace: >> (XEN) [<ffff828c8011b7b7>] check_lock+0x3d/0x49 >> (XEN) [<ffff828c8011ba2f>] _spin_lock_irqsave+0x21/0x53 >> (XEN) [<ffff828c80161187>] pci_conf_read+0x37/0xd0 >> (XEN) >> (XEN) >> (XEN) **************************************** >> (XEN) Panic on CPU 0: >> (XEN) Xen BUG at spinlock.c:24 >> (XEN) **************************************** >> (XEN) >> (XEN) Reboot in five seconds... >> > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel

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