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From:   Yury Norov <yury.norov@gmail.com>
To:     Yury Norov <yury.norov@gmail.com>,
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Subject: [PATCH 15/54] arch/x86: replace cpumask_weight with cpumask_empty where appropriate
Date:   Sun, 23 Jan 2022 10:38:46 -0800
Message-Id: <20220123183925.1052919-16-yury.norov@gmail.com>
In-Reply-To: <20220123183925.1052919-1-yury.norov@gmail.com>
References: <20220123183925.1052919-1-yury.norov@gmail.com>
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In some cases, arch/x86 code calls cpumask_weight() to check if any bit of
a given cpumask is set. We can do it 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>
---
 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 b57b3db9a6a7..e23ff03290b8 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 933a2ebad471..c3317f0650d8 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 1e9ff28bc2e0..ea277fc08357 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);
-- 
2.30.2