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

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 83f901e..f276aff 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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);