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 1E162C4332F for ; Tue, 8 Nov 2022 14:10:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235235AbiKHOKe (ORCPT ); Tue, 8 Nov 2022 09:10:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235221AbiKHOKZ (ORCPT ); Tue, 8 Nov 2022 09:10:25 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E402BE3E for ; Tue, 8 Nov 2022 06:10:25 -0800 (PST) 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 DDC68B81ADD for ; Tue, 8 Nov 2022 14:10:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3FFDBC433D6; Tue, 8 Nov 2022 14:10:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667916622; bh=nq4UgCZmyk/lK7YPl7EC7xPDrq3VLutyMjvQdih1IHs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jXlevkJVKfe+cDnozQH4cu8RejguJ8j+sxNGQ3Mrk6uPiXB+l8xMKGHj9HXujPbxu IJGILbTPGrW3GajFVGJl2ErpjWzKUpebKglSLEwWGySbyR8i1u2WUUAWMNeDmXfOil +owzg8VyRTw3I/JQO6hSzfDWIImD7x6mTDz7nTlY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Jason A. Donenfeld" , Florian Fainelli , Herbert Xu , Sasha Levin Subject: [PATCH 6.0 080/197] hwrng: bcm2835 - use hwrng_msleep() instead of cpu_relax() Date: Tue, 8 Nov 2022 14:38:38 +0100 Message-Id: <20221108133358.480641824@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221108133354.787209461@linuxfoundation.org> References: <20221108133354.787209461@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@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 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; -- 2.35.1