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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7104BC43219 for ; Fri, 3 May 2019 20:32:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 410772075C for ; Fri, 3 May 2019 20:32:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="bwsPLUjE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727150AbfECUcb (ORCPT ); Fri, 3 May 2019 16:32:31 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:36591 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726480AbfECUc2 (ORCPT ); Fri, 3 May 2019 16:32:28 -0400 Received: by mail-wr1-f65.google.com with SMTP id o4so9366020wra.3 for ; Fri, 03 May 2019 13:32:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=yFWs26NyTQBBHnTLimY9fErMEAAd/wEGYGdh8uiAhr0=; b=bwsPLUjEVmFYODhU+c2MOxzIKK3emyjBG6iCWkMYBqFtQoZdtIYr6hP52/jRNoLJo3 eWFwTsZ2fupPL6Yoij/cbTqbcsRY+MzOnQEEKtNsW53PcpsKck2s4WkmtNdIqAiaXUAy E3mzAvJqLybY/fO/hL8AAASs3qDmwPdkVMzVPx2N1Y41P4Mbq+zvb+n2nkupMjvO1YqX 0kDWD4Vcls4ZVIQ5kCgjh7EeAMPRqNNgVglP9OP3zyMjI8L2apKkMVzj7JNQKHSmwlun gj4oDbVZVohDucTN1kUJOHCyBXUxoVk1ncVAOn3CjBu//3/hgcrBaoVvgGOLCygDOHzl nQrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=yFWs26NyTQBBHnTLimY9fErMEAAd/wEGYGdh8uiAhr0=; b=BcOe0B8u01Oez2E7sNX5JuKkSM7QRtrxNVsM4CcvknqY9hH/klRevYfTlMx7uJZdCz VB0q9l44xhvBevBbpth6M32ncmnqJ2/TRhdPk0YhCHqNvspUZzZSb2NUU/W0XodLSEYz l3fURG29wENLF3nqF1nBLhxvjrylUwN4uWQMp0DK7RGt90RhoO0WhuuNs8K63Ma6+l8E mLDjZWKSMhrTnQ/vnFklNJNu4xX6JNTe5WAOcN53Jqdh4mtuZ49JVjO5apVzbt2ssLh5 3pBD4MjxEtyv8Neo8pm60/WcwvIuvwG1TaG2S+sVrQ4L/biAWXDmbiNCod4GUOdzJWAp ITaQ== X-Gm-Message-State: APjAAAUf5/lmdEEDe+Dl1WyWtx7tINdm52ygqRAWU2PWwOp4eKaUzxoR elCG3X3pNJIvBapQ9XtJYw1r+T0FL78= X-Google-Smtp-Source: APXvYqydkBhECIudeVFVl1XOv4VNXeL9LFJR4eBdis9OQQ3nSkYQIomuAj4y2ShR8eFhfGxf0ZXcjA== X-Received: by 2002:adf:fd04:: with SMTP id e4mr8683562wrr.145.1556915546193; Fri, 03 May 2019 13:32:26 -0700 (PDT) Received: from [192.168.0.41] (sju31-1-78-210-255-2.fbx.proxad.net. [78.210.255.2]) by smtp.googlemail.com with ESMTPSA id e8sm4779602wrc.96.2019.05.03.13.32.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 May 2019 13:32:25 -0700 (PDT) Subject: Re: [PATCH 7/7] clocksource/arm_arch_timer: Use arch_timer_read_counter to access stable counters To: Valentin Schneider , Marc Zyngier , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Russell King , Will Deacon , Catalin Marinas , Mark Rutland , Wim Van Sebroeck , Guenter Roeck References: <20190408154907.223536-1-marc.zyngier@arm.com> <20190408154907.223536-8-marc.zyngier@arm.com> <2a60a031-1eab-2d5e-89ff-b5d516545eeb@linaro.org> From: Daniel Lezcano Message-ID: Date: Fri, 3 May 2019 22:32:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Valentin, On 30/04/2019 17:39, Valentin Schneider wrote: > Hi, > > On 30/04/2019 16:27, Marc Zyngier wrote: > [...] >>>> @@ -372,6 +392,7 @@ static u32 notrace sun50i_a64_read_cntv_tval_el0(void) >>>> DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *, timer_unstable_counter_workaround); >>>> EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround); >>>> >>>> +static atomic_t timer_unstable_counter_workaround_in_use = ATOMIC_INIT(0); >>> >>> Wouldn't make sense to READ_ONCE / WRITE_ONCE instead of using an atomic? >> >> I don't think *_ONCE says anything about the atomicity of the access. It >> only instruct the compiler that this should only be accessed once, and >> not reloaded/rewritten. > > FWIW 7bd3e239d6c6 ("locking: Remove atomicy checks from {READ,WRITE}_ONCE") > points this out. Interesting, thanks for the pointer. -- Daniel -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog 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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1D44C43219 for ; Fri, 3 May 2019 20:32:43 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 8E66F2081C for ; Fri, 3 May 2019 20:32:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="n/AUz9Uc"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="bwsPLUjE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E66F2081C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=86AJ9GtpH+IYDfAHzpl7Vh6MbwQjRsD7o9m2hj+Wu/0=; b=n/AUz9UcuDWz9S NPjxKfIYwYInN+AbLSlUfvZbUv4plh1vP8mIBypz11NxVsk0J+YbheXpHxb0oQ2GjgEkNSc9uf6F1 hOQsPlVHZ7YE0yHCInBIu/8fvdo34rGnG9e6DMQ8PDg2aU7dHyRPvLs5t3Okh17XRgk3qbePFPU37 2EFWnf9EVeXxeq+adP4c0OVa3y+uAMyieKF4gAEr7Vdf3e9TTaUwx53IZShNQe/SY6TkoZNrwdRn7 0x3FTi6S2muqz6xEmsvY2Y0twtGysBvW+u1IezidZf7DdO5by0dxxZHmv060kQwQHxi+QdLOV5g/s TAQ3jm21+vcb7yCbVtuA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hMer9-0001Dx-Bw; Fri, 03 May 2019 20:32:31 +0000 Received: from mail-wr1-x442.google.com ([2a00:1450:4864:20::442]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hMer5-0001Ct-P5 for linux-arm-kernel@lists.infradead.org; Fri, 03 May 2019 20:32:29 +0000 Received: by mail-wr1-x442.google.com with SMTP id d22so2229891wrb.4 for ; Fri, 03 May 2019 13:32:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=yFWs26NyTQBBHnTLimY9fErMEAAd/wEGYGdh8uiAhr0=; b=bwsPLUjEVmFYODhU+c2MOxzIKK3emyjBG6iCWkMYBqFtQoZdtIYr6hP52/jRNoLJo3 eWFwTsZ2fupPL6Yoij/cbTqbcsRY+MzOnQEEKtNsW53PcpsKck2s4WkmtNdIqAiaXUAy E3mzAvJqLybY/fO/hL8AAASs3qDmwPdkVMzVPx2N1Y41P4Mbq+zvb+n2nkupMjvO1YqX 0kDWD4Vcls4ZVIQ5kCgjh7EeAMPRqNNgVglP9OP3zyMjI8L2apKkMVzj7JNQKHSmwlun gj4oDbVZVohDucTN1kUJOHCyBXUxoVk1ncVAOn3CjBu//3/hgcrBaoVvgGOLCygDOHzl nQrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=yFWs26NyTQBBHnTLimY9fErMEAAd/wEGYGdh8uiAhr0=; b=YQoXTa2lv+qhjhzeFXwfbrFxNoZuUg2zU06Qx9weQyRq8gPKKs1TSQh0n+C6vV33D+ /ii+yoywX1U9vwJsAc3LfRm4AsEERbXeykmQ3XT1qjlyDaHlEMgFc4AXoAzApG2qzs2m ZjqyEhFuIeMV2ugMbx57GKA61Dhb984Emp3zLqSQdd5XtXZuSpLbqDnogjKtBtw2C4Wr xHNwtd/og2yEFTM4iyDc6K4+/zCeuW/eK9klzFhQvf129toFo05mtfO6yqFz79tcvJiR CXlf4Ns02EsF+2iPCPxGqkCqIlVuX+AGiguEzHzQyZUI4DdIK4P6/8z0FB9iM2ahu+fC Hu/Q== X-Gm-Message-State: APjAAAXpqR0o12TS9Rh9sX93gjfbbvQoeycyFGl8oimqtcUZqjz3YCdQ /SIbWLdO/TJEHcI1Zcnn3x8xwA== X-Google-Smtp-Source: APXvYqydkBhECIudeVFVl1XOv4VNXeL9LFJR4eBdis9OQQ3nSkYQIomuAj4y2ShR8eFhfGxf0ZXcjA== X-Received: by 2002:adf:fd04:: with SMTP id e4mr8683562wrr.145.1556915546193; Fri, 03 May 2019 13:32:26 -0700 (PDT) Received: from [192.168.0.41] (sju31-1-78-210-255-2.fbx.proxad.net. [78.210.255.2]) by smtp.googlemail.com with ESMTPSA id e8sm4779602wrc.96.2019.05.03.13.32.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 May 2019 13:32:25 -0700 (PDT) Subject: Re: [PATCH 7/7] clocksource/arm_arch_timer: Use arch_timer_read_counter to access stable counters To: Valentin Schneider , Marc Zyngier , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20190408154907.223536-1-marc.zyngier@arm.com> <20190408154907.223536-8-marc.zyngier@arm.com> <2a60a031-1eab-2d5e-89ff-b5d516545eeb@linaro.org> From: Daniel Lezcano Message-ID: Date: Fri, 3 May 2019 22:32:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190503_133227_813204_E34DC0FC X-CRM114-Status: GOOD ( 15.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Russell King , Catalin Marinas , Will Deacon , Wim Van Sebroeck , Guenter Roeck Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org CkhpIFZhbGVudGluLAoKT24gMzAvMDQvMjAxOSAxNzozOSwgVmFsZW50aW4gU2NobmVpZGVyIHdy b3RlOgo+IEhpLAo+IAo+IE9uIDMwLzA0LzIwMTkgMTY6MjcsIE1hcmMgWnluZ2llciB3cm90ZToK PiBbLi4uXQo+Pj4+IEBAIC0zNzIsNiArMzkyLDcgQEAgc3RhdGljIHUzMiBub3RyYWNlIHN1bjUw aV9hNjRfcmVhZF9jbnR2X3R2YWxfZWwwKHZvaWQpCj4+Pj4gIERFRklORV9QRVJfQ1BVKGNvbnN0 IHN0cnVjdCBhcmNoX3RpbWVyX2VycmF0dW1fd29ya2Fyb3VuZCAqLCB0aW1lcl91bnN0YWJsZV9j b3VudGVyX3dvcmthcm91bmQpOwo+Pj4+ICBFWFBPUlRfU1lNQk9MX0dQTCh0aW1lcl91bnN0YWJs ZV9jb3VudGVyX3dvcmthcm91bmQpOwo+Pj4+ICAKPj4+PiArc3RhdGljIGF0b21pY190IHRpbWVy X3Vuc3RhYmxlX2NvdW50ZXJfd29ya2Fyb3VuZF9pbl91c2UgPSBBVE9NSUNfSU5JVCgwKTsKPj4+ Cj4+PiBXb3VsZG4ndCBtYWtlIHNlbnNlIHRvIFJFQURfT05DRSAvIFdSSVRFX09OQ0UgaW5zdGVh ZCBvZiB1c2luZyBhbiBhdG9taWM/Cj4+Cj4+IEkgZG9uJ3QgdGhpbmsgKl9PTkNFIHNheXMgYW55 dGhpbmcgYWJvdXQgdGhlIGF0b21pY2l0eSBvZiB0aGUgYWNjZXNzLiBJdAo+PiBvbmx5IGluc3Ry dWN0IHRoZSBjb21waWxlciB0aGF0IHRoaXMgc2hvdWxkIG9ubHkgYmUgYWNjZXNzZWQgb25jZSwg YW5kCj4+IG5vdCByZWxvYWRlZC9yZXdyaXR0ZW4uCj4gCj4gRldJVyA3YmQzZTIzOWQ2YzYgKCJs b2NraW5nOiBSZW1vdmUgYXRvbWljeSBjaGVja3MgZnJvbSB7UkVBRCxXUklURX1fT05DRSIpCj4g cG9pbnRzIHRoaXMgb3V0LgoKSW50ZXJlc3RpbmcsIHRoYW5rcyBmb3IgdGhlIHBvaW50ZXIuCgog IC0tIERhbmllbAoKCi0tIAogPGh0dHA6Ly93d3cubGluYXJvLm9yZy8+IExpbmFyby5vcmcg4pSC IE9wZW4gc291cmNlIHNvZnR3YXJlIGZvciBBUk0gU29DcwoKRm9sbG93IExpbmFybzogIDxodHRw Oi8vd3d3LmZhY2Vib29rLmNvbS9wYWdlcy9MaW5hcm8+IEZhY2Vib29rIHwKPGh0dHA6Ly90d2l0 dGVyLmNvbS8jIS9saW5hcm9vcmc+IFR3aXR0ZXIgfAo8aHR0cDovL3d3dy5saW5hcm8ub3JnL2xp bmFyby1ibG9nLz4gQmxvZwoKCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fCmxpbnV4LWFybS1rZXJuZWwgbWFpbGluZyBsaXN0CmxpbnV4LWFybS1rZXJuZWxA bGlzdHMuaW5mcmFkZWFkLm9yZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xp c3RpbmZvL2xpbnV4LWFybS1rZXJuZWwK