{"id":22946,"url":"https://patchwork.libcamera.org/api/1.1/patches/22946/?format=json","web_url":"https://patchwork.libcamera.org/patch/22946/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/1.1/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20250310170326.185273-1-barnabas.pocze@ideasonboard.com>","date":"2025-03-10T17:03:26","name":"[v1] libcamera: v4l2_videodevice: `lastUsedCounter_` need not be atomic","commit_ref":null,"pull_url":null,"state":"accepted","archived":false,"hash":"6c174dddf2bba907665416be2d43a00ade774769","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/1.1/people/216/?format=json","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/22946/mbox/","series":[{"id":5054,"url":"https://patchwork.libcamera.org/api/1.1/series/5054/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5054","date":"2025-03-10T17:03:26","name":"[v1] libcamera: v4l2_videodevice: `lastUsedCounter_` need not be atomic","version":1,"mbox":"https://patchwork.libcamera.org/series/5054/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/22946/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/22946/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 30301C32F1\n\tfor ;\n\tMon, 10 Mar 2025 17:03:36 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id D2753687FA;\n\tMon, 10 Mar 2025 18:03:35 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id F36B7687F0\n\tfor ;\n\tMon, 10 Mar 2025 18:03:33 +0100 (CET)","from pb-laptop.local (185.221.143.221.nat.pool.zt.hu\n\t[185.221.143.221])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 489CA227\n\tfor ;\n\tMon, 10 Mar 2025 18:01:56 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"SzGFI+nB\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1741626117;\n\tbh=u2Km0sfP+5a7CydMFT5g/+2GpinsHbRIKaubxO57OYQ=;\n\th=From:To:Subject:Date:From;\n\tb=SzGFI+nB0MKu8rAPITK55oB0pH2bEnBfIp1mVlpYFhS1evDcvqhF/DSiiai3y3C4N\n\tt2YuNxjs+v2BJXGfTmwtzgep+Q2lG9Xp6x1btIw7qIfJWA7iM6WQE6k2Y7XCbqp47+\n\t846w+gE4W808ObSJ/Ny1v8nqXWoFituMym1VeQFk=","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","To":"libcamera-devel@lists.libcamera.org","Subject":"[PATCH v1] libcamera: v4l2_videodevice: `lastUsedCounter_` need not\n\tbe atomic","Date":"Mon, 10 Mar 2025 18:03:26 +0100","Message-ID":"<20250310170326.185273-1-barnabas.pocze@ideasonboard.com>","X-Mailer":"git-send-email 2.48.1","MIME-Version":"1.0","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"8bit","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "},"content":"The `V4L2BufferCache` type is not thread-safe. Its `lastUsedCounter_`\nmember is not used in contexts where its atomicity would matter.\nSo it does not need to be have an atomic type.\n\nSigned-off-by: Barnabás Pőcze \n---\n include/libcamera/internal/v4l2_videodevice.h | 2 +-\n src/libcamera/v4l2_videodevice.cpp | 4 ++--\n 2 files changed, 3 insertions(+), 3 deletions(-)","diff":"diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h\nindex f021c2a01..e52b50c67 100644\n--- a/include/libcamera/internal/v4l2_videodevice.h\n+++ b/include/libcamera/internal/v4l2_videodevice.h\n@@ -158,7 +158,7 @@ private:\n \t\tstd::vector planes_;\n \t};\n \n-\tstd::atomic lastUsedCounter_;\n+\tuint64_t lastUsedCounter_;\n \tstd::vector cache_;\n \t/* \\todo Expose the miss counter through an instrumentation API. */\n \tunsigned int missCounter_;\ndiff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp\nindex e241eb47b..f5b3fa09d 100644\n--- a/src/libcamera/v4l2_videodevice.cpp\n+++ b/src/libcamera/v4l2_videodevice.cpp\n@@ -190,7 +190,7 @@ V4L2BufferCache::V4L2BufferCache(const std::vector>\n {\n \tfor (const std::unique_ptr &buffer : buffers)\n \t\tcache_.emplace_back(true,\n-\t\t\t\t lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),\n+\t\t\t\t lastUsedCounter_++,\n \t\t\t\t *buffer.get());\n }\n \n@@ -258,7 +258,7 @@ int V4L2BufferCache::get(const FrameBuffer &buffer)\n \t\treturn -ENOENT;\n \n \tcache_[use] = Entry(false,\n-\t\t\t lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),\n+\t\t\t lastUsedCounter_++,\n \t\t\t buffer);\n \n \treturn use;\n","prefixes":["v1"]}