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    SubjectRe: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock
    On 07/13/2010 01:23 PM, Peter Palfrader wrote:
    > Sorry for the delay.
    >

    A good trace is worth it.

    > [<ffffffff810373c0>] ? child_rip+0x0/0x20
    > Code: 78 4f 44 89 e1 48 d3 e0 44 89 f2 48 f7 e2 48 0f ac d0 20 4a 8d 0c 38 44 39 03 75 a4 48 8b 15 15 df 6b 00 48 39 ca 77 17 48 89 d0<f0> 48 0f b1 0d 04 df 6b 00 48 39 c1 48 89 c2 75 e7 48 89 ca 48
    > RIP [<ffffffff81054f73>] pvclock_clocksource_read+0x83/0xc0
    > RSP<ffff88007fb47880>
    > CR2: ffffffff81712e80
    > ---[ end trace 38f25e02ae34d4c1 ]---
    > BUG: unable to handle kernel paging request at ffffffff81712e80
    > IP: [<ffffffff81054f73>] pvclock_clocksource_read+0x83/0xc0
    > PGD 1003067 PUD 1007063 PMD 7e8b1063 PTE 8000000001712161
    >

    Read-only pte

    > Oops: 0003 [#2] SMP
    >

    Write fault.

    > Code: 78 4f 44 89 e1 48 d3 e0 44 89 f2 48 f7 e2 48 0f ac d0 20 4a 8d 0c 38 44 39 03 75 a4 48 8b 15 15 df 6b 00 48 39 ca 77 17 48 89 d0<f0> 48 0f b1 0d 04 df 6b 00 48 39 c1 48 89 c2 75 e7 48 89 ca 48
    > RIP [<ffffffff81054f73>] pvclock_clocksource_read+0x83/0xc0
    >

    --> lock cmpxchg %rcx,0x6bdf04(%rip)

    > static atomic64_t last_value = ATOMIC64_INIT(0);
    >
    > cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
    > {
    >

    [...]

    > last = atomic64_read(&last_value);
    > do {
    > if (ret < last)
    > return last;
    > last = atomic64_cmpxchg(&last_value, last, ret);
    > } while (unlikely(last != ret));
    >
    > return ret;
    > }

    So it looks like last_value was placed in a read only section. Please
    post your System.map somewhere.

    --
    error compiling committee.c: too many arguments to function



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