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    Subject[tip: x86/cleanups] x86: Replace cpumask_weight() with cpumask_empty() where appropriate
    The following commit has been merged into the x86/cleanups branch of tip:

    Commit-ID: 3a5ff1f6dd50f5e1c2aa87491910dd6d275af24b
    Gitweb: https://git.kernel.org/tip/3a5ff1f6dd50f5e1c2aa87491910dd6d275af24b
    Author: Yury Norov <yury.norov@gmail.com>
    AuthorDate: Thu, 10 Feb 2022 14:49:00 -08:00
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitterDate: Sun, 10 Apr 2022 22:35:38 +02:00

    x86: Replace cpumask_weight() with cpumask_empty() where appropriate

    In some cases, x86 code calls cpumask_weight() to check if any bit of a
    given cpumask is set.

    This can be done more efficiently with cpumask_empty() because
    cpumask_empty() stops traversing the cpumask as soon as it finds first set
    bit, while cpumask_weight() counts all bits unconditionally.

    Signed-off-by: Yury Norov <yury.norov@gmail.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
    Link: https://lore.kernel.org/r/20220210224933.379149-17-yury.norov@gmail.com

    ---
    arch/x86/kernel/cpu/resctrl/rdtgroup.c | 14 +++++++-------
    arch/x86/mm/mmio-mod.c | 2 +-
    arch/x86/platform/uv/uv_nmi.c | 2 +-
    3 files changed, 9 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
    index 83f901e..f276aff 100644
    --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
    +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
    @@ -341,14 +341,14 @@ static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,

    /* Check whether cpus belong to parent ctrl group */
    cpumask_andnot(tmpmask, newmask, &prgrp->cpu_mask);
    - if (cpumask_weight(tmpmask)) {
    + if (!cpumask_empty(tmpmask)) {
    rdt_last_cmd_puts("Can only add CPUs to mongroup that belong to parent\n");
    return -EINVAL;
    }

    /* Check whether cpus are dropped from this group */
    cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask);
    - if (cpumask_weight(tmpmask)) {
    + if (!cpumask_empty(tmpmask)) {
    /* Give any dropped cpus to parent rdtgroup */
    cpumask_or(&prgrp->cpu_mask, &prgrp->cpu_mask, tmpmask);
    update_closid_rmid(tmpmask, prgrp);
    @@ -359,7 +359,7 @@ static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
    * and update per-cpu rmid
    */
    cpumask_andnot(tmpmask, newmask, &rdtgrp->cpu_mask);
    - if (cpumask_weight(tmpmask)) {
    + if (!cpumask_empty(tmpmask)) {
    head = &prgrp->mon.crdtgrp_list;
    list_for_each_entry(crgrp, head, mon.crdtgrp_list) {
    if (crgrp == rdtgrp)
    @@ -394,7 +394,7 @@ static int cpus_ctrl_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,

    /* Check whether cpus are dropped from this group */
    cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask);
    - if (cpumask_weight(tmpmask)) {
    + if (!cpumask_empty(tmpmask)) {
    /* Can't drop from default group */
    if (rdtgrp == &rdtgroup_default) {
    rdt_last_cmd_puts("Can't drop CPUs from default group\n");
    @@ -413,12 +413,12 @@ static int cpus_ctrl_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
    * and update per-cpu closid/rmid.
    */
    cpumask_andnot(tmpmask, newmask, &rdtgrp->cpu_mask);
    - if (cpumask_weight(tmpmask)) {
    + if (!cpumask_empty(tmpmask)) {
    list_for_each_entry(r, &rdt_all_groups, rdtgroup_list) {
    if (r == rdtgrp)
    continue;
    cpumask_and(tmpmask1, &r->cpu_mask, tmpmask);
    - if (cpumask_weight(tmpmask1))
    + if (!cpumask_empty(tmpmask1))
    cpumask_rdtgrp_clear(r, tmpmask1);
    }
    update_closid_rmid(tmpmask, rdtgrp);
    @@ -488,7 +488,7 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,

    /* check that user didn't specify any offline cpus */
    cpumask_andnot(tmpmask, newmask, cpu_online_mask);
    - if (cpumask_weight(tmpmask)) {
    + if (!cpumask_empty(tmpmask)) {
    ret = -EINVAL;
    rdt_last_cmd_puts("Can only assign online CPUs\n");
    goto unlock;
    diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
    index 933a2eb..c3317f0 100644
    --- a/arch/x86/mm/mmio-mod.c
    +++ b/arch/x86/mm/mmio-mod.c
    @@ -400,7 +400,7 @@ static void leave_uniprocessor(void)
    int cpu;
    int err;

    - if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
    + if (!cpumask_available(downed_cpus) || cpumask_empty(downed_cpus))
    return;
    pr_notice("Re-enabling CPUs...\n");
    for_each_cpu(cpu, downed_cpus) {
    diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c
    index 1e9ff28..ea277fc 100644
    --- a/arch/x86/platform/uv/uv_nmi.c
    +++ b/arch/x86/platform/uv/uv_nmi.c
    @@ -985,7 +985,7 @@ static int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)

    /* Clear global flags */
    if (master) {
    - if (cpumask_weight(uv_nmi_cpu_mask))
    + if (!cpumask_empty(uv_nmi_cpu_mask))
    uv_nmi_cleanup_mask();
    atomic_set(&uv_nmi_cpus_in_nmi, -1);
    atomic_set(&uv_nmi_cpu, -1);
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