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 83C1FFA3743 for ; Tue, 1 Nov 2022 11:38:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231440AbiKALiI (ORCPT ); Tue, 1 Nov 2022 07:38:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231394AbiKALhb (ORCPT ); Tue, 1 Nov 2022 07:37:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BDE61DA52; Tue, 1 Nov 2022 04:32:13 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id B3C25615F0; Tue, 1 Nov 2022 11:31:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4911C433C1; Tue, 1 Nov 2022 11:31:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667302290; bh=M/wlWrMuFWFlNr4cnsXihNBkIiZ9hHBkCDu2Fk/tOZw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UOBW37F2q1EM/m3W/6nvvTT2d9oIhOeBe2/OLzWEvH9jnqxpm+KWVR02FRmF2tqI1 olMtrsmY/sCgDD9adXPFSPPMgNMzQ3ZH5FIBNScF5U/pEFevxWDnWR6k5XxCtIVFqn EqIV4u37hlAxAxhFkVZyPh4GQK1VESL7otz0ZgfVQjIxvzP27fyzQMWOu0dt33msfg 375tm+9EP8zhqmkeWC4ZGzhD3BC5FdS4mhDiWzuSOgWbx6/ZRrIOUBAJp6rpWZtBu0 5D86plw6WowrUxWkEinDaK3I+hcXAAmJ/pmIEXfSM2gc28u2Wx3PONNwsJ2t8Q3BrD L5oT/8vdBNI5Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Jason A. Donenfeld" , Florian Fainelli , Herbert Xu , Sasha Levin , olivia@selenic.com, rjui@broadcom.com, sbranden@broadcom.com, linux-crypto@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH AUTOSEL 4.19 4/6] hwrng: bcm2835 - use hwrng_msleep() instead of cpu_relax() Date: Tue, 1 Nov 2022 07:31:14 -0400 Message-Id: <20221101113118.800889-4-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221101113118.800889-1-sashal@kernel.org> References: <20221101113118.800889-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Jason A. Donenfeld" [ Upstream commit 96cb9d0554457086664d3bd10630b11193d863f1 ] 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 Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- 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 19bde680aee1..56c38edf9fac 100644 --- a/drivers/char/hw_random/bcm2835-rng.c +++ b/drivers/char/hw_random/bcm2835-rng.c @@ -72,7 +72,7 @@ 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; -- 2.35.1