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    Subject[PATCH 4.4 095/192] [PATCH 099/135] Drivers: hv: vmbus: dont manipulate with clocksources on crash
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    [ Upstream commit 3ccb4fd8f492f99aece21acc1bd6142275f26236 ]

    clocksource_change_rating() involves mutex usage and can't be called
    in interrupt context. It also makes sense to avoid doing redundant work
    on crash.

    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/hv/hv.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    --- a/drivers/hv/hv.c
    +++ b/drivers/hv/hv.c
    @@ -293,8 +293,14 @@ void hv_cleanup(void)
    * Cleanup the TSC page based CS.
    */
    if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
    - clocksource_change_rating(&hyperv_cs_tsc, 10);
    - clocksource_unregister(&hyperv_cs_tsc);
    + /*
    + * Crash can happen in an interrupt context and unregistering
    + * a clocksource is impossible and redundant in this case.
    + */
    + if (!oops_in_progress) {
    + clocksource_change_rating(&hyperv_cs_tsc, 10);
    + clocksource_unregister(&hyperv_cs_tsc);
    + }

    hypercall_msr.as_uint64 = 0;
    wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);

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