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    Subject[ 11/46] xen/time: Fix kasprintf splat when allocating timer%d IRQ line.
    Date
    3.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

    commit 7918c92ae9638eb8a6ec18e2b4a0de84557cccc8 upstream.

    When we online the CPU, we get this splat:

    smpboot: Booting Node 0 Processor 1 APIC 0x2
    installing Xen timer for CPU 1
    BUG: sleeping function called from invalid context at /home/konrad/ssd/konrad/linux/mm/slab.c:3179
    in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/1
    Pid: 0, comm: swapper/1 Not tainted 3.9.0-rc6upstream-00001-g3884fad #1
    Call Trace:
    [<ffffffff810c1fea>] __might_sleep+0xda/0x100
    [<ffffffff81194617>] __kmalloc_track_caller+0x1e7/0x2c0
    [<ffffffff81303758>] ? kasprintf+0x38/0x40
    [<ffffffff813036eb>] kvasprintf+0x5b/0x90
    [<ffffffff81303758>] kasprintf+0x38/0x40
    [<ffffffff81044510>] xen_setup_timer+0x30/0xb0
    [<ffffffff810445af>] xen_hvm_setup_cpu_clockevents+0x1f/0x30
    [<ffffffff81666d0a>] start_secondary+0x19c/0x1a8

    The solution to that is use kasprintf in the CPU hotplug path
    that 'online's the CPU. That is, do it in in xen_hvm_cpu_notify,
    and remove the call to in xen_hvm_setup_cpu_clockevents.

    Unfortunatly the later is not a good idea as the bootup path
    does not use xen_hvm_cpu_notify so we would end up never allocating
    timer%d interrupt lines when booting. As such add the check for
    atomic() to continue.

    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/xen/enlighten.c | 5 ++++-
    arch/x86/xen/time.c | 6 +++++-
    2 files changed, 9 insertions(+), 2 deletions(-)

    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -1365,8 +1365,11 @@ static int __cpuinit xen_hvm_cpu_notify(
    switch (action) {
    case CPU_UP_PREPARE:
    xen_vcpu_setup(cpu);
    - if (xen_have_vector_callback)
    + if (xen_have_vector_callback) {
    xen_init_lock_cpu(cpu);
    + if (xen_feature(XENFEAT_hvm_safe_pvclock))
    + xen_setup_timer(cpu);
    + }
    break;
    default:
    break;
    --- a/arch/x86/xen/time.c
    +++ b/arch/x86/xen/time.c
    @@ -482,7 +482,11 @@ static void xen_hvm_setup_cpu_clockevent
    {
    int cpu = smp_processor_id();
    xen_setup_runstate_info(cpu);
    - xen_setup_timer(cpu);
    + /*
    + * xen_setup_timer(cpu) - snprintf is bad in atomic context. Hence
    + * doing it xen_hvm_cpu_notify (which gets called by smp_init during
    + * early bootup and also during CPU hotplug events).
    + */
    xen_setup_cpu_clockevents();
    }




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