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=-10.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 01F23C04EBF for ; Wed, 5 Dec 2018 09:54:44 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C55B820661 for ; Wed, 5 Dec 2018 09:54:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="VQTYgdqE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C55B820661 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=6X189g4qYrYhoMLYzf+Ru0CQwnBXlqqUyQEmCVzCkdY=; b=VQTYgdqEAUuM8Z qn9zaWz0USyB3bunLtsLUWfYot3jgrwCv/wVQTBOT1M/oU4O9+Jb9D62TUhThU5Qfd/OsAnNpUu6F wgszxJvYmkX4SqeVX2LCK3R8V5Zd/MrKqutz0YtPnm6RcltDO/OZgcOd7J321p5AGLzqyxiTo79EJ ozcnMAQZt8+5C2MykW56vewYti0LFq4761rfeos/ut1HAfhDlUoWXiRzJkuYk5ANH9IJ4Sxu9JoVc FhjrcHMlkhl/VJ1DWf1I6Fx0doRaqN4myWGeljbJ4EWJF5S9J06ddkv+gGMftCzagTrXeKgC3YO32 a/y2B83AXgFRoBB7vD+w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gUTtA-00073r-Fh; Wed, 05 Dec 2018 09:54:40 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gUTt7-0006rF-Ar for linux-arm-kernel@lists.infradead.org; Wed, 05 Dec 2018 09:54:38 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 276EC80D; Wed, 5 Dec 2018 01:54:26 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id EB5443F575; Wed, 5 Dec 2018 01:54:25 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 974C51AE0BA8; Wed, 5 Dec 2018 09:54:46 +0000 (GMT) Date: Wed, 5 Dec 2018 09:54:46 +0000 From: Will Deacon To: Anders Roxell Subject: Re: [PATCH v2] tracing: add cond_resched to ftrace_replace_code() Message-ID: <20181205095445.GA14317@arm.com> References: <20181204192903.8193-1-anders.roxell@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20181204192903.8193-1-anders.roxell@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181205_015437_388074_C42943EB X-CRM114-Status: GOOD ( 20.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: keescook@chromium.org, arnd@arndb.de, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, mingo@redhat.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Anders, Steve, On Tue, Dec 04, 2018 at 08:29:03PM +0100, Anders Roxell wrote: > When running in qemu on an kernel built with allmodconfig and debug > options (in particular kcov and ubsan) enabled, ftrace_replace_code > function call take minutes. The ftrace selftest calls > ftrace_replace_code to look >40000 through > ftrace_make_call/ftrace_make_nop, and these end up calling > __aarch64_insn_write/aarch64_insn_patch_text_nosync. > > Microseconds add up because this is called in a loop for each dyn_ftrace > record, and this triggers the softlockup watchdog unless we let it sleep > occasionally. > > Rework so that we call cond_resched() if !irqs_disabled() && !preempt_count(). > > Suggested-by: Steven Rostedt (VMware) > Signed-off-by: Anders Roxell > --- > kernel/trace/ftrace.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index c375e33239f7..7080eb464983 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -2419,11 +2419,19 @@ void __weak ftrace_replace_code(int enable) > { > struct dyn_ftrace *rec; > struct ftrace_page *pg; > + bool schedulable; > int failed; > > if (unlikely(ftrace_disabled)) > return; > > + /* > + * Some archs calls this function with interrupts or preemption > + * disabled. However, for other archs that can preempt, this can cause > + * an tremendous unneeded latency. > + */ > + schedulable = !irqs_disabled() && !preempt_count(); Is there a reason not to use preemptible() here? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel