From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E6DA533CDF for ; Wed, 15 Nov 2023 19:45:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BcVOHiIx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99C65C433C7; Wed, 15 Nov 2023 19:45:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700077505; bh=SIExlMmjH0bu1F2dMklpBW6AkVPofe+CTdo9XOl0epY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BcVOHiIxGCyLOKn0BjudfNRgjd0y8waHVcGzLvX99HXEpV1GX29NYZ2Ub06qE8zEl TqeTRQ2sVEDAyTN4sb7JbvW9KLkIrmvwCSQm7eFI9FRCf9fZnVEyzYqLoXCh9J4bRs 1SZL+TLVa7Byz8bpSH4WQydnpq4Hgrc0maN6FYTs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stefan Wahren , "Jason A. Donenfeld" , Herbert Xu , Sasha Levin Subject: [PATCH 6.6 344/603] hwrng: bcm2835 - Fix hwrng throughput regression Date: Wed, 15 Nov 2023 14:14:49 -0500 Message-ID: <20231115191637.328391157@linuxfoundation.org> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20231115191613.097702445@linuxfoundation.org> References: <20231115191613.097702445@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stefan Wahren [ Upstream commit b58a36008bfa1aadf55f516bcbfae40c779eb54b ] The last RCU stall fix caused a massive throughput regression of the hwrng on Raspberry Pi 0 - 3. hwrng_msleep doesn't sleep precisely enough and usleep_range doesn't allow scheduling. So try to restore the best possible throughput by introducing hwrng_yield which interruptable sleeps for one jiffy. Some performance measurements on Raspberry Pi 3B+ (arm64/defconfig): sudo dd if=/dev/hwrng of=/dev/null count=1 bs=10000 cpu_relax ~138025 Bytes / sec hwrng_msleep(1000) ~13 Bytes / sec hwrng_yield ~2510 Bytes / sec Fixes: 96cb9d055445 ("hwrng: bcm2835 - use hwrng_msleep() instead of cpu_relax()") Link: https://lore.kernel.org/linux-arm-kernel/bc97ece5-44a3-4c4e-77da-2db3eb66b128@gmx.net/ Signed-off-by: Stefan Wahren Reviewed-by: Jason A. Donenfeld Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- drivers/char/hw_random/bcm2835-rng.c | 2 +- drivers/char/hw_random/core.c | 6 ++++++ include/linux/hw_random.h | 1 + 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c index e19b0f9f48b97..4c08efe7f3753 100644 --- a/drivers/char/hw_random/bcm2835-rng.c +++ b/drivers/char/hw_random/bcm2835-rng.c @@ -70,7 +70,7 @@ 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; - hwrng_msleep(rng, 1000); + hwrng_yield(rng); } num_words = rng_readl(priv, RNG_STATUS) >> 24; diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index e3598ec9cfca8..420f155d251fb 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -678,6 +678,12 @@ long hwrng_msleep(struct hwrng *rng, unsigned int msecs) } EXPORT_SYMBOL_GPL(hwrng_msleep); +long hwrng_yield(struct hwrng *rng) +{ + return wait_for_completion_interruptible_timeout(&rng->dying, 1); +} +EXPORT_SYMBOL_GPL(hwrng_yield); + static int __init hwrng_modinit(void) { int ret; diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h index 8a3115516a1ba..136e9842120e8 100644 --- a/include/linux/hw_random.h +++ b/include/linux/hw_random.h @@ -63,5 +63,6 @@ extern void hwrng_unregister(struct hwrng *rng); extern void devm_hwrng_unregister(struct device *dve, struct hwrng *rng); extern long hwrng_msleep(struct hwrng *rng, unsigned int msecs); +extern long hwrng_yield(struct hwrng *rng); #endif /* LINUX_HWRANDOM_H_ */ -- 2.42.0