From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 591D02E36FD for ; Mon, 4 Aug 2025 06:00:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754287228; cv=none; b=hN/DEzOaCvQrSTG1wjIqPskAyJ0qrpVGw0g7RETFOhtrg+q7Y4YsXKWn0cm/tc/1zYPuyu1iOMnrYikl1S0M3f92ETiG+UWA4z8lgREd+biFH3NsQUPD07ucKN1sgzqPrZXcBbzJGHozH+ZI/m/vvlz4fX+rp2YfjE32ABlrDqc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754287228; c=relaxed/simple; bh=CMjSVsnlYIHATz4fXgWOQlWXjlcbst7J2k2mwNhi1Uk=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=MjAzYMkjQ8DpZcdBbb6vKOPPAKxHo0BWowVdvchys4/CoxFUmtUVCPJlxNxvH1ofML5uaeTUwBAEeONyBZhkPrSnGu9rp/vFfz5MWjCgPgGr374C9Lc6s2/USwUZ9yHnzgNYaIAaF+E6ZSa4MOYv4dhFzyB8zBVBGdY4lj1+rjg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=TnWiv36G; arc=none smtp.client-ip=209.85.214.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TnWiv36G" Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-2403c13cac3so38019415ad.0 for ; Sun, 03 Aug 2025 23:00:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1754287227; x=1754892027; darn=vger.kernel.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=GW9ee20vQhs+179oAZihQfxJ7e5GO7cvFv5OZiXPnJ8=; b=TnWiv36GJTMN+9LQBBxwj5Xn6WHAy3zy4tIIwg0kjzdME24J3ZeIZAKReLxDuxNlDe E/p+rHScsM2OFr4c63KFFV5Qj17x/VKMMpichsnt8AVNW7jbBwhyp1jHLn+TJdQc509v AJ3tn+ZLtfDT/oTuBuyejYdGerDFADZYFOioNpK6pj2JDfaOGw4gE8YQJZ8pWBs9bdjT W1nJD6QElDxf++YghWNBM4/MlXvyMXuc1UvkCw1pBHDQMdYDcUhwg8RcCmrJ/9Ai/P83 v4zN2+2BPKl+b4byb8fEdPt2uaTB9MpDUe5rmeIpuGu5PamWm89T+rgYVLnIMwS3xG8Y usdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754287227; x=1754892027; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=GW9ee20vQhs+179oAZihQfxJ7e5GO7cvFv5OZiXPnJ8=; b=FTkUoSee6JpWK2lcJKITMpqWFsN5gD+FnaPvUHyl+UVz3OY4va3faKlnrO5xBbGlts uze6793x6LJ1nfjWd8sYFTE1pJf4jn6i5r2scM6VjEO59JJTbm9zjnSU0KxlBpF09aT3 JM3dDGDWXndO5ek354Bg5nlDGyxsRHVAisD+LRZpaZXShYYOLZYCGlOGpoxLFB7/u85K wqUjeGbBaaocs3+ee8MLOluYA1i6QUN+BXBkeppNbo40VwhNLbBa2kl1ot8UO+DVJI3y ECYXdVA5qPQ09uTrRiFbXPOGEDH05Jw0PeT5fa8Il9uNBfCN97mgEYNHxEb+rcnIuCnT BKug== X-Forwarded-Encrypted: i=1; AJvYcCVCxDg/CsDP6dazbDTNXALbCrzoluX8ICINC/QeLcoM1CSLexg2e90FnR6GROMXhgkIbIjAyPcTDZc=@vger.kernel.org X-Gm-Message-State: AOJu0Yz3PiyEVKpqxF2F1F8GQFb/0RiAXSNA+x8RNDL5y7YZ0UvX0fMT V9DoD3IqVaCyWwqDLiISqyzkh7m9COtk6tUoLlqKR/S0PpP5oDwS3bWy06vkEeXUGMZK9NCAKPa uzgUtPsqmt0l6M1MDu/CesIcfj+fC1kUxxpYU5HX0 X-Gm-Gg: ASbGnctdbVPkZByZJjuWufuo6LdYd9iNRuhNTv86EyULlzt4MYkIkgj7NqRoZGskTVI JL447wb08+kkO6YpvkcoG9bNjzG2xEqzPFO4sm/wrsPxHwD6zQybF3c/TmhUGvbzxXjAUyxA1/A 1EYtUkmrGuxTDw23bwsS8jsOAPLyErtodwaqnFnOAXObpkP6fzbg94eulJQTuQw7H37OzFJ9FHF J3B7quLXOJOdHXGH+KOyKo5Y1CyZdmqzCl8RtM= X-Google-Smtp-Source: AGHT+IGjk2UIBetcSl3cOr+lPMFKsmxl+eJNheNEbJC3BP4ucecQ/KCFqsi7V58RFGF5MsVFqR2tEo7P/NgkM0Cjsno= X-Received: by 2002:a17:902:8601:b0:23f:ed0f:8dd4 with SMTP id d9443c01a7336-24200d7d3a1mr165647385ad.23.1754287226255; Sun, 03 Aug 2025 23:00:26 -0700 (PDT) Precedence: bulk X-Mailing-List: workflows@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250803180558.2967962-1-soham.bagchi@utah.edu> In-Reply-To: <20250803180558.2967962-1-soham.bagchi@utah.edu> From: Marco Elver Date: Mon, 4 Aug 2025 08:00:00 +0200 X-Gm-Features: Ac12FXzqJppzOFmhwA4bjarsTDBlyoRY0yvvampHjfyILSAANQCwWK9R6F2pkOY Message-ID: Subject: Re: [PATCH v2] kcov: load acquire coverage count in user-space code To: Soham Bagchi Cc: akpm@linux-foundation.org, andreyknvl@gmail.com, arnd@arndb.de, corbet@lwn.net, dvyukov@google.com, glider@google.com, kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, sohambagchi@outlook.com, tglx@linutronix.de, workflows@vger.kernel.org Content-Type: text/plain; charset="UTF-8" On Sun, 3 Aug 2025 at 20:06, Soham Bagchi wrote: > > Updating the KCOV documentation to use a load-acquire > operation for the first element of the shared memory > buffer between kernel-space and user-space. > > The load-acquire pairs with the write memory barrier > used in kcov_move_area() > > Signed-off-by: Soham Bagchi Reviewed-by: Marco Elver > --- > > Changes in v2: Btw, it is customary to send out the whole patch series on a version bump, even if only one of the patches changed. https://www.kernel.org/doc/html/latest/process/submitting-patches.html#explicit-in-reply-to-headers > - note for load-acquire shifted to block comment > in code rather than in the preceding paragraphs > --- > Documentation/dev-tools/kcov.rst | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/Documentation/dev-tools/kcov.rst b/Documentation/dev-tools/kcov.rst > index 6611434e2dd..40a4b500073 100644 > --- a/Documentation/dev-tools/kcov.rst > +++ b/Documentation/dev-tools/kcov.rst > @@ -361,7 +361,12 @@ local tasks spawned by the process and the global task that handles USB bus #1: > */ > sleep(2); > > - n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED); > + /* > + * The load to the coverage count should be an acquire to pair with > + * pair with the corresponding write memory barrier (smp_wmb()) on > + * the kernel-side in kcov_move_area(). > + */ > + n = __atomic_load_n(&cover[0], __ATOMIC_ACQUIRE); > for (i = 0; i < n; i++) > printf("0x%lx\n", cover[i + 1]); > if (ioctl(fd, KCOV_DISABLE, 0)) > -- > 2.34.1 >