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 0C8FD215F73; Wed, 4 Dec 2024 23:36:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733355366; cv=none; b=edpKC5G9v5o16PyKdu9Khw1Y4Tofz4+LunvxljBdFwkQK8lGJ9o5ThcDDkqBcSIxauYuyvTUecUnAdWheIYXQ6dJfwRZq24w+diWTESHNf8w08HUX8NGN1mauBRG5daJe0iu0R8mwOeGR8hEWZSht2c+3LwAIj+HpZsWta0MUIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733355366; c=relaxed/simple; bh=4CDcnZ1VSNENRhki7AXY4PqO+Rl1qVnKdD6EHA5I00s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mPsIxwl4qPg9DFeNkte2J1VxzpFF0gbYAWzL74TH6AIzTqXtD0rmRI20U5yk5ENxYSi20uhU6geZIVdOBdUbtfR7VntGquWO0xzV4Bd0mGaQSh3FckeksZqgcvXIEvhASnGZ8k5o1qYvIBV9nwlHb7JmVcfeIQG0E1RxN9EUKNs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z1OmDpHD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z1OmDpHD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D365C4CED2; Wed, 4 Dec 2024 23:36:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733355365; bh=4CDcnZ1VSNENRhki7AXY4PqO+Rl1qVnKdD6EHA5I00s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z1OmDpHDqSLAnrVswR33eNIs1I/nk7zg9w1vmgLJ/Fr579RJMyLXISolcHtyF9aao yn1xhJVfCxAmABBwK+8lsSYBhxvE5V+VCq4nnDumMQFdzgxaAPLcSltyZWdHnALITj Le7Ko/f9j2IdxyfftCMs0aQwWLEo1/EWHgDJ8B+Y+LtmbCl55ElLyLczLua2wU1xsj TGFS9cpcJ70gnReya21ks/x10rkBcf4oTuhJryV2/TFQRaSBRaXXglp3L0hXT751CY 7tNTe2CZXooqJcgqX9l+2iXQB9+h2TxsrVhpkue0fAFTVCgf5OMkYUvTERXuqZFiZ7 QLIADbswJarDw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Dmitry Torokhov , =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= , Alexandre Belloni , Sasha Levin , linux-rtc@vger.kernel.org Subject: [PATCH AUTOSEL 6.1 2/4] rtc: cmos: avoid taking rtc_lock for extended period of time Date: Wed, 4 Dec 2024 17:24:34 -0500 Message-ID: <20241204222444.2250332-2-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241204222444.2250332-1-sashal@kernel.org> References: <20241204222444.2250332-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.119 Content-Transfer-Encoding: 8bit From: Dmitry Torokhov [ Upstream commit 0a6efab33eab4e973db26d9f90c3e97a7a82e399 ] On my device reading entirety of /sys/devices/pnp0/00:03/cmos_nvram0/nvmem takes about 9 msec during which time interrupts are off on the CPU that does the read and the thread that performs the read can not be migrated or preempted by another higher priority thread (RT or not). Allow readers and writers be preempted by taking and releasing rtc_lock spinlock for each individual byte read or written rather than once per read/write request. Signed-off-by: Dmitry Torokhov Reviewed-by: Mateusz Jończyk Link: https://lore.kernel.org/r/Zxv8QWR21AV4ztC5@google.com Signed-off-by: Alexandre Belloni Signed-off-by: Sasha Levin --- drivers/rtc/rtc-cmos.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c index 542568cd72b32..5f43773900d18 100644 --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -645,18 +645,17 @@ static int cmos_nvram_read(void *priv, unsigned int off, void *val, unsigned char *buf = val; off += NVRAM_OFFSET; - spin_lock_irq(&rtc_lock); - for (; count; count--, off++) { + for (; count; count--, off++, buf++) { + guard(spinlock_irq)(&rtc_lock); if (off < 128) - *buf++ = CMOS_READ(off); + *buf = CMOS_READ(off); else if (can_bank2) - *buf++ = cmos_read_bank2(off); + *buf = cmos_read_bank2(off); else - break; + return -EIO; } - spin_unlock_irq(&rtc_lock); - return count ? -EIO : 0; + return 0; } static int cmos_nvram_write(void *priv, unsigned int off, void *val, @@ -671,23 +670,23 @@ static int cmos_nvram_write(void *priv, unsigned int off, void *val, * NVRAM to update, updating checksums is also part of its job. */ off += NVRAM_OFFSET; - spin_lock_irq(&rtc_lock); - for (; count; count--, off++) { + for (; count; count--, off++, buf++) { /* don't trash RTC registers */ if (off == cmos->day_alrm || off == cmos->mon_alrm || off == cmos->century) - buf++; - else if (off < 128) - CMOS_WRITE(*buf++, off); + continue; + + guard(spinlock_irq)(&rtc_lock); + if (off < 128) + CMOS_WRITE(*buf, off); else if (can_bank2) - cmos_write_bank2(*buf++, off); + cmos_write_bank2(*buf, off); else - break; + return -EIO; } - spin_unlock_irq(&rtc_lock); - return count ? -EIO : 0; + return 0; } /*----------------------------------------------------------------*/ -- 2.43.0