From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0778EC433E6 for ; Tue, 12 Jan 2021 23:02:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD3A823130 for ; Tue, 12 Jan 2021 23:02:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2395110AbhALXBy (ORCPT ); Tue, 12 Jan 2021 18:01:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732525AbhALXBo (ORCPT ); Tue, 12 Jan 2021 18:01:44 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0D4EC061795 for ; Tue, 12 Jan 2021 15:01:03 -0800 (PST) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1610492462; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=V3VcMaNAnS5DFS8St8UE1/STiFhKNlHQt73PRBf24+I=; b=DaPLP/NyAVXZL/ViHl/ajSDvUjI7+Boqj3dZaKoFmbxjA7rwaMtJ3VNFptqyxnRgmSh8fL 4D6H65dZ5DIVlhPsVnQH5UNunk3ea4vkuLLm1luJiFzZ5iekKKzSNjznYsG3oYfvOUp0Ec NigSKAAKJl4j6z9Boq5GBeWgt1mZ0qubUkajFrqNo1cB2w0NYvkE67tLVvREVVAG9ENpPh VL1PKr+SFQKNh3Mkp7H6RZrDKGZsNbkyDU1eC8INrYk+CL7cDK+bA8pGVG6KG9c20bdpd4 qR6u1k3Vvt2WHf9zIzCFK0TF0eUsr5KoAmOnPeMIkr9Ba7BteKKewBY0kMYuGQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1610492462; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=V3VcMaNAnS5DFS8St8UE1/STiFhKNlHQt73PRBf24+I=; b=VzPCGit3Dro7aVwCOgfbmJ3XybyEyQSCFs9WRuVjYIST7GSoq5PVnoTa8WUuVLNBhXZpYt quTmgDNwgUTyx1Ag== To: linux-kernel@vger.kernel.org Cc: Steven Rostedt , Ingo Molnar , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH 2/3] tracing: Use in_serving_softirq() to deduct softirq status. Date: Wed, 13 Jan 2021 00:00:56 +0100 Message-Id: <20210112230057.2374308-3-bigeasy@linutronix.de> In-Reply-To: <20210112230057.2374308-1-bigeasy@linutronix.de> References: <20210112230057.2374308-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org PREEMPT_RT does not report "serving softirq" because the tracing core looks at the preemption counter while PREEMPT_RT does not update it while processing softirqs in order to remain preemptible. The information is stored somewhere else. The in_serving_softirq() macro and the SOFTIRQ_OFFSET define are still working but not on the preempt-counter. Use in_serving_softirq() macro which works on PREEMPT_RT. On !PREEMPT_RT the compiler (gcc-10 / clang-11) is smart enough to optimize the in_serving_softirq() related read of the preemption counter away. The only difference I noticed by using in_serving_softirq() on !PREEMPT_RT is that gcc-10 implemented tracing_gen_ctx_flags() as reading FLAG, jmp _tracing_gen_ctx_flags(). Without in_serving_softirq() it inlined _tracing_gen_ctx_flags() into tracing_gen_ctx_flags(). Signed-off-by: Sebastian Andrzej Siewior --- kernel/trace/trace.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 679112d3b3da9..416b63e05960e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2596,8 +2596,7 @@ unsigned int _tracing_gen_ctx_flags(unsigned long irq= flags) trace_flags |=3D TRACE_FLAG_NMI; if (pc & HARDIRQ_MASK) trace_flags |=3D TRACE_FLAG_HARDIRQ; - - if (pc & SOFTIRQ_OFFSET) + if (in_serving_softirq()) trace_flags |=3D TRACE_FLAG_SOFTIRQ; =20 if (tif_need_resched()) --=20 2.30.0