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    Subject[PATCH 4.14 047/138] staging: lustre: disable preempt while sampling processor id.
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: NeilBrown <neilb@suse.com>


    [ Upstream commit dbeccabf5294e80f7cc9ee566746c42211bed736 ]

    Calling smp_processor_id() without disabling preemption
    triggers a warning (if CONFIG_DEBUG_PREEMPT).
    I think the result of cfs_cpt_current() is only used as a hint for
    load balancing, rather than as a precise and stable indicator of
    the current CPU. So it doesn't need to be called with
    preemption disabled.

    So disable preemption inside cfs_cpt_current() to silence the warning.

    Signed-off-by: NeilBrown <neilb@suse.com>
    Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++++++------
    1 file changed, 7 insertions(+), 6 deletions(-)

    --- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
    +++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
    @@ -528,19 +528,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node);
    int
    cfs_cpt_current(struct cfs_cpt_table *cptab, int remap)
    {
    - int cpu = smp_processor_id();
    - int cpt = cptab->ctb_cpu2cpt[cpu];
    + int cpu;
    + int cpt;

    - if (cpt < 0) {
    - if (!remap)
    - return cpt;
    + preempt_disable();
    + cpu = smp_processor_id();
    + cpt = cptab->ctb_cpu2cpt[cpu];

    + if (cpt < 0 && remap) {
    /* don't return negative value for safety of upper layer,
    * instead we shadow the unknown cpu to a valid partition ID
    */
    cpt = cpu % cptab->ctb_nparts;
    }
    -
    + preempt_enable();
    return cpt;
    }
    EXPORT_SYMBOL(cfs_cpt_current);

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