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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F113DC4332F for ; Mon, 13 Dec 2021 10:35:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237169AbhLMKfn (ORCPT ); Mon, 13 Dec 2021 05:35:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234875AbhLMKfA (ORCPT ); Mon, 13 Dec 2021 05:35:00 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83E40C08E857 for ; Mon, 13 Dec 2021 02:08:56 -0800 (PST) Date: Mon, 13 Dec 2021 11:08:53 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1639390135; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XaXdr5ZWdr10AhuPnIf/lbNihptCfanKMNKhs551A28=; b=SV7m6MniIPaioBum9eYilmWyx2ULBbokWfMCOwheg0jbD4wANZm0bEYM8+vAA9P0Hb28ih bCF7OYQzKOPXhoQyyisE1JYNKxTfr6xOS9RkcVFpMJZb4jSy2DfLO7/ok5AYI6ocpoBbv1 Zin4N8NGpouZ493eVULmyZT/l4nKnW6HXW3oRaKJ7ty7VfOeQf5dQS4J8NILc7KZLlPZtQ pS2qpA2Fyx7KAxQCCQG1FKk81za0dU2NnZh8dexbSxmlSGMQMt8DiJygh5Lz5mj7eR092n l0SowiYJTw04bc/D1MhhmhwgPs5tZay6SKnZlu9vok/TCwuX062A2LlIGFbNWA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1639390135; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XaXdr5ZWdr10AhuPnIf/lbNihptCfanKMNKhs551A28=; b=sM6WJm7mm/HBoN0AnuS0TC3b7vcrKno11zDVQVNzTTxhhrAkb42H37TBeuo7FrDwXhvi0w OhoidyDZYZRyZ3Dg== From: Sebastian Andrzej Siewior To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Thomas Gleixner Subject: [PATCH v2] tracing: Account bottom half disabled sections. Message-ID: References: <20211210203240.43a8e7eb@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Disabling only bottom halves via local_bh_disable() disables also preemption but this remains invisible to tracing. On a CONFIG_PREEMPT kernel one might wonder why there is no scheduling happening despite the N flag in the trace. The reason might be the a rcu_read_lock_bh() section. Add a 'b' to the tracing output if in task context with disabled bottom halves. Signed-off-by: Sebastian Andrzej Siewior --- v1=E2=80=A6v2: - Move output to the IRQ-off section. include/linux/trace_events.h | 1 + kernel/trace/trace.c | 6 ++++-- kernel/trace/trace_output.c | 4 ++++ 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 2d167ac3452c5..a2af7e1156eac 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -172,6 +172,7 @@ enum trace_flag_type { TRACE_FLAG_SOFTIRQ =3D 0x10, TRACE_FLAG_PREEMPT_RESCHED =3D 0x20, TRACE_FLAG_NMI =3D 0x40, + TRACE_FLAG_BH_OFF =3D 0x80, }; =20 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88de94da596b1..c3618dd7ecb4b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2601,6 +2601,8 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int ir= qs_status) trace_flags |=3D TRACE_FLAG_HARDIRQ; if (in_serving_softirq()) trace_flags |=3D TRACE_FLAG_SOFTIRQ; + if (softirq_count() >> (SOFTIRQ_SHIFT + 1)) + trace_flags |=3D TRACE_FLAG_BH_OFF; =20 if (tif_need_resched()) trace_flags |=3D TRACE_FLAG_NEED_RESCHED; @@ -4183,7 +4185,7 @@ unsigned long trace_total_entries(struct trace_array = *tr) static void print_lat_help_header(struct seq_file *m) { seq_puts(m, "# _------=3D> CPU# \n" - "# / _-----=3D> irqs-off \n" + "# / _-----=3D> irqs-off/BH-disabled\n" "# | / _----=3D> need-resched \n" "# || / _---=3D> hardirq/softirq \n" "# ||| / _--=3D> preempt-depth \n" @@ -4224,7 +4226,7 @@ static void print_func_help_header_irq(struct array_b= uffer *buf, struct seq_file =20 print_event_info(buf, m); =20 - seq_printf(m, "# %.*s _-----=3D> irqs-off\n",= prec, space); + seq_printf(m, "# %.*s _-----=3D> irqs-off/BH-= disabled\n", prec, space); seq_printf(m, "# %.*s / _----=3D> need-resched= \n", prec, space); seq_printf(m, "# %.*s| / _---=3D> hardirq/soft= irq\n", prec, space); seq_printf(m, "# %.*s|| / _--=3D> preempt-dept= h\n", prec, space); diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 3547e7176ff79..8aa493d25c73e 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -445,14 +445,18 @@ int trace_print_lat_fmt(struct trace_seq *s, struct t= race_entry *entry) char irqs_off; int hardirq; int softirq; + int bh_off; int nmi; =20 nmi =3D entry->flags & TRACE_FLAG_NMI; hardirq =3D entry->flags & TRACE_FLAG_HARDIRQ; softirq =3D entry->flags & TRACE_FLAG_SOFTIRQ; + bh_off =3D entry->flags & TRACE_FLAG_BH_OFF; =20 irqs_off =3D + (entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' : (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : + bh_off ? 'b' : (entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' : '.'; =20 --=20 2.34.1