From nobody Sat Apr 11 02:18:40 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DA2BC28B2B for ; Wed, 17 Aug 2022 13:09:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239635AbiHQNJ4 (ORCPT ); Wed, 17 Aug 2022 09:09:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239712AbiHQNJZ (ORCPT ); Wed, 17 Aug 2022 09:09:25 -0400 Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCDB462F2 for ; Wed, 17 Aug 2022 06:08:17 -0700 (PDT) Received: by mail-wr1-x42b.google.com with SMTP id a4so4424419wrq.1 for ; Wed, 17 Aug 2022 06:08:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc; bh=yZJd/ZKQ9mlwmL6Q+KyC3+p6JDQdyYFK//6TmktPmuw=; b=HERUzvZz3x8ABix1FIP+TbJTfGTZSruRspdVloO6vi7RWmlGqoJmzN70Ij2hspbPJT c5ruJI2w1d72QpHUIQzNapLkpbd8W+R5kUpQq8OZy/xpjSxyFxwUjqUq4Ll0aNS62fLX Hp5m43Zhd4CWh+N0k3+kP+yqyekOnt+SSewVnnNM9rBGfWRwvG4tRgfzOzRIZCMu0COE 0Mc3H0y+J1cNy349Zq0uBntKkGLFXnrQTUe3DoIpBRuSgua891UW+ZP5P8M2fODV9MGb RVlTmADNsfLN3L2Z/67fCbGQfG6IMOinMxBcHwqCVpI6AVRgvqgXcWKDLolIgbSbcjHc TdHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc; bh=yZJd/ZKQ9mlwmL6Q+KyC3+p6JDQdyYFK//6TmktPmuw=; b=RfCNqjuVmZN4JuJCJLce5Oz1IqKPinu9jtLy1GGF80v85HApSYgXtXqPuUOsBIX5z3 S0vVSMHqRm5oc+VZ6HNPQze42qrUJQLBpQDp272hMZ0fxf/D09Gz64OQA5aF9MFKR3kX o4N5E2JO0WW5tafonEuuIWKCX3qLzfR24BTeiYAYzQzqE7huOcOf4fkQvzqukFBE1o12 jpfpPerr/uTXODLd6rmdHI8Xd0r7BjVKCD5N1aTLTPwDOSnLXqcipr/fchrq9UGrDvSi dNMVPjoLxiYmXpL2tsd1D3ElDe8goHTuQbqVBhQ7VrhYtgpEmSlc6fuiFxK+zBBN1LWI rYVw== X-Gm-Message-State: ACgBeo0SaeRrNgr1TatDExifek5XQ3fYSEWvC3i0LJB/03k7aPJQhkaQ t44AJZQ1YnlvnMK/2o5Yhz5PNpk23M0/ww== X-Google-Smtp-Source: AA6agR7Bz9c08dnhsKjG95ErmPIkScVNcf3tP2jSx1acZbBbcuGlSunXlydBesdvB/bT9w9X0zBFsQ== X-Received: by 2002:adf:e710:0:b0:225:109d:456d with SMTP id c16-20020adfe710000000b00225109d456dmr5510742wrm.589.1660741695800; Wed, 17 Aug 2022 06:08:15 -0700 (PDT) Received: from localhost ([109.180.234.208]) by smtp.gmail.com with ESMTPSA id j25-20020a05600c1c1900b003a5ce167a68sm2198796wms.7.2022.08.17.06.08.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Aug 2022 06:08:14 -0700 (PDT) From: Punit Agrawal To: ast@kernel.org Cc: Punit Agrawal , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, zhoufeng.zf@bytedance.com, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, jolsa@kernel.org Subject: [PATCH] bpf: Simplify code by using for_each_cpu_wrap() Date: Wed, 17 Aug 2022 14:08:07 +0100 Message-Id: <20220817130807.68279-1-punit.agrawal@bytedance.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In the percpu freelist code, it is a common pattern to iterate over the possible CPUs mask starting with the current CPU. The pattern is implemented using a hand rolled while loop with the loop variable increment being open-coded. Simplify the code by replacing the while() loops with for_each_cpu_wrap() helper to iterate over the possible cpus starting with the current CPU. As a result, some of the special-casing in the loop also gets simplified. No functional change intended. Signed-off-by: Punit Agrawal --- Hi, I noticed an opportunity for simplifying the code while reviewing a backport for one of the commits in this area. Please consider merging. Thanks, Punit kernel/bpf/percpu_freelist.c | 42 ++++++++++-------------------------- 1 file changed, 11 insertions(+), 31 deletions(-) diff --git a/kernel/bpf/percpu_freelist.c b/kernel/bpf/percpu_freelist.c index 00b874c8e889..9dd9201c6f07 100644 --- a/kernel/bpf/percpu_freelist.c +++ b/kernel/bpf/percpu_freelist.c @@ -56,10 +56,9 @@ static inline bool pcpu_freelist_try_push_extra(struct p= cpu_freelist *s, static inline void ___pcpu_freelist_push_nmi(struct pcpu_freelist *s, struct pcpu_freelist_node *node) { - int cpu, orig_cpu; + int cpu; =20 - orig_cpu =3D cpu =3D raw_smp_processor_id(); - while (1) { + for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) { struct pcpu_freelist_head *head; =20 head =3D per_cpu_ptr(s->freelist, cpu); @@ -68,15 +67,10 @@ static inline void ___pcpu_freelist_push_nmi(struct pcp= u_freelist *s, raw_spin_unlock(&head->lock); return; } - cpu =3D cpumask_next(cpu, cpu_possible_mask); - if (cpu >=3D nr_cpu_ids) - cpu =3D 0; - - /* cannot lock any per cpu lock, try extralist */ - if (cpu =3D=3D orig_cpu && - pcpu_freelist_try_push_extra(s, node)) - return; } + + /* cannot lock any per cpu lock, try extralist */ + pcpu_freelist_try_push_extra(s, node); } =20 void __pcpu_freelist_push(struct pcpu_freelist *s, @@ -125,13 +119,12 @@ static struct pcpu_freelist_node *___pcpu_freelist_po= p(struct pcpu_freelist *s) { struct pcpu_freelist_head *head; struct pcpu_freelist_node *node; - int orig_cpu, cpu; + int cpu; =20 - orig_cpu =3D cpu =3D raw_smp_processor_id(); - while (1) { + for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) { head =3D per_cpu_ptr(s->freelist, cpu); if (!READ_ONCE(head->first)) - goto next_cpu; + continue; raw_spin_lock(&head->lock); node =3D head->first; if (node) { @@ -140,12 +133,6 @@ static struct pcpu_freelist_node *___pcpu_freelist_pop= (struct pcpu_freelist *s) return node; } raw_spin_unlock(&head->lock); -next_cpu: - cpu =3D cpumask_next(cpu, cpu_possible_mask); - if (cpu >=3D nr_cpu_ids) - cpu =3D 0; - if (cpu =3D=3D orig_cpu) - break; } =20 /* per cpu lists are all empty, try extralist */ @@ -164,13 +151,12 @@ ___pcpu_freelist_pop_nmi(struct pcpu_freelist *s) { struct pcpu_freelist_head *head; struct pcpu_freelist_node *node; - int orig_cpu, cpu; + int cpu; =20 - orig_cpu =3D cpu =3D raw_smp_processor_id(); - while (1) { + for_each_cpu_wrap(cpu, cpu_possible_mask, raw_smp_processor_id()) { head =3D per_cpu_ptr(s->freelist, cpu); if (!READ_ONCE(head->first)) - goto next_cpu; + continue; if (raw_spin_trylock(&head->lock)) { node =3D head->first; if (node) { @@ -180,12 +166,6 @@ ___pcpu_freelist_pop_nmi(struct pcpu_freelist *s) } raw_spin_unlock(&head->lock); } -next_cpu: - cpu =3D cpumask_next(cpu, cpu_possible_mask); - if (cpu >=3D nr_cpu_ids) - cpu =3D 0; - if (cpu =3D=3D orig_cpu) - break; } =20 /* cannot pop from per cpu lists, try extralist */ --=20 2.35.1