From patchwork Mon Oct 10 15:06:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 13002690 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 7B66BC433F5 for ; Mon, 10 Oct 2022 15:07:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Cc:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=CrIpqpdI3cbaM9uurE2TVc62QtQAImJ4gVYNsSJIv34=; b=3CG9bqesYwuLqE yBQbLUY0PvdfmK7sMR76O3BFc8obnsohr+oXinLdOZ3sZ3xxEAnlhJWf9i3yS2DUsPWm2tgMDAeFp SBfd062swNZwDELj66lr3HZhWQOYM1S/sJKKN6eASUqrPGEjB9BiVfxTpeNVxixP4Qx/Jzrg1zKeS hU5EuiX41M8Xz1QOBlYI2+89QsRDeDQt+3E3TslcB8U3lSR/OWWNh+4Y7p81odLopdiiaV7AK7fFF PrxYgy41hQ8TaaMJxonxSDJda8ZuNoEKBkSCeI2uCJWj3BX+/FIOU86+5FMxNe9f2oN7dob7UJyBh ogPmheyxuW+aCqh7YILA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ohuMS-001Iee-TC; Mon, 10 Oct 2022 15:06:33 +0000 Received: from ams.source.kernel.org ([2604:1380:4601:e00::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ohuMP-001Idy-Pu; Mon, 10 Oct 2022 15:06:31 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 2C899B80EBC; Mon, 10 Oct 2022 15:06:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0B6FC433D7; Mon, 10 Oct 2022 15:06:25 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="WdldBTLp" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1665414384; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2/cGOeCsidGmGiZ98DVF3Ta98rQRXE0YgnqKqi0mssQ=; b=WdldBTLpA+rEApH5WA9tf36Hzezz6L/S61/QOnUnaZye2OC8euwQFFIFduPA4qHcj89EtS ZckhCfAU4w5rX6PVyZVpxemHJ0uliGXUobYUxofMpuPPrp9G9dZJBY/tu3VId3UxCJNlg/ A1w42QeozC5SmPuwWYnfBe9rvdagFp0= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 89a9ed2b (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 10 Oct 2022 15:06:23 +0000 (UTC) From: "Jason A. Donenfeld" To: Mark Brown , Florian Fainelli , "Jason A. Donenfeld" , Dominik Brodowski , Herbert Xu , kernelci-results@groups.io, bot@kernelci.org, gtucker@collabora.com, linux-arm-kernel@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] hw_random: bcm2835: use hwrng_msleep() instead of cpu_relax() Date: Mon, 10 Oct 2022 09:06:07 -0600 Message-Id: <20221010150607.720600-1-Jason@zx2c4.com> In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221010_080630_154649_75A6A96E X-CRM114-Status: GOOD ( 15.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Rather than busy looping, yield back to the scheduler and sleep for a bit in the event that there's no data. This should hopefully prevent the stalls that Mark reported: <6>[ 3.362859] Freeing initrd memory: 16196K <3>[ 23.160131] rcu: INFO: rcu_sched self-detected stall on CPU <3>[ 23.166057] rcu: 0-....: (2099 ticks this GP) idle=03b4/1/0x40000002 softirq=28/28 fqs=1050 <4>[ 23.174895] (t=2101 jiffies g=-1147 q=2353 ncpus=4) <4>[ 23.180203] CPU: 0 PID: 49 Comm: hwrng Not tainted 6.0.0 #1 <4>[ 23.186125] Hardware name: BCM2835 <4>[ 23.189837] PC is at bcm2835_rng_read+0x30/0x6c <4>[ 23.194709] LR is at hwrng_fillfn+0x71/0xf4 <4>[ 23.199218] pc : [] lr : [] psr: 40000033 <4>[ 23.205840] sp : f093df70 ip : 00000000 fp : 00000000 <4>[ 23.211404] r10: c3c7e800 r9 : 00000000 r8 : c17e6b20 <4>[ 23.216968] r7 : c17e6b64 r6 : c18b0a74 r5 : c07ccd99 r4 : c3f171c0 <4>[ 23.223855] r3 : 000fffff r2 : 00000040 r1 : c3c7e800 r0 : c3f171c0 <4>[ 23.230743] Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA Thumb Segment none <4>[ 23.238426] Control: 50c5387d Table: 0020406a DAC: 00000051 <4>[ 23.244519] CPU: 0 PID: 49 Comm: hwrng Not tainted 6.0.0 #1 Link: https://lore.kernel.org/all/Y0QJLauamRnCDUef@sirena.org.uk/ Signed-off-by: Jason A. Donenfeld Acked-by: Florian Fainelli --- I haven't tested this. Somebody with access to that kernel CI infra that triggered this will need to test. drivers/char/hw_random/bcm2835-rng.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c index e7dd457e9b22..e98fcac578d6 100644 --- a/drivers/char/hw_random/bcm2835-rng.c +++ b/drivers/char/hw_random/bcm2835-rng.c @@ -71,7 +71,7 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max, while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) { if (!wait) return 0; - cpu_relax(); + hwrng_msleep(rng, 1000); } num_words = rng_readl(priv, RNG_STATUS) >> 24;