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=-8.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 9B641C4727F for ; Wed, 23 Sep 2020 01:44:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 48079238D7 for ; Wed, 23 Sep 2020 01:44:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600825444; bh=/mv7XWqTiYWR6o/xSPo8s1q3xMl8+80d4aWHfAsgsvc=; h=From:To:Cc:Subject:Date:List-ID:From; b=oaAhQGkprmie51nXOVg0jY9PmVgxz4tYDnqRbRqz1rpE4RqBgCMReihcLUbSI6yX1 FUyo0mRN2Rl1q5jYkwWmKfUCQ4F6pE34jPr5jGv2CFYAtDnYGbqNKtvEi/d8B39K7u 9nEE/eUHPdL2LQWc5PHMuPl4lnPh3LRCDD44xUj0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727076AbgIWBoD (ORCPT ); Tue, 22 Sep 2020 21:44:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56754 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727074AbgIWBn7 (ORCPT ); Tue, 22 Sep 2020 21:43:59 -0400 Received: from mail-oi1-x243.google.com (mail-oi1-x243.google.com [IPv6:2607:f8b0:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A7B9C0613D1 for ; Tue, 22 Sep 2020 18:43:59 -0700 (PDT) Received: by mail-oi1-x243.google.com with SMTP id v20so23285036oiv.3 for ; Tue, 22 Sep 2020 18:43:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=jS6qXoxP8oaPPr4z/ISWBa/fqTB0t5njLCtqvmesqnQ=; b=G+hI5wX8b2Mgi7CpmlZz/BbRZ94AkUl88hXN1JwuQ34ehWFDDAH1EiGJlznX6Q1hkh leoTF4ALmGHjcSFCGWQTp9oolzWxQJAfHjJcY2uTD8jw1//YObslhst7+G02nWz+wJ6H SamX0bagHIpt+fJ/d7+7oToKKwlqUc5BpPiJY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=jS6qXoxP8oaPPr4z/ISWBa/fqTB0t5njLCtqvmesqnQ=; b=DNJQ1c2L//bv9KCDNBUB5YYINW2N3IM2S2USgImRBCW8VP0bETMD4ZDukD47EYXTdY mWgeobkj6m+SN8HrrqcpGcNWpLcOmztoXiQ2cW1eu0SeyWARBtAvF4HGzYfmoqI8DR1a tId6JJGq6X5KRM1EYBf3RO9cLwuAi1IcajOOr0L6V5KjDtuRN6TqX9kyUZtntbwUW7bZ ELz0rNKzka/dNaiTwVaRWQQICOzYPGzbGqCZAHvRuYFTxYPGbrmf08XGDslsFTbNTKWR oWKMxDUOoQJlEKPhVJiX3BEnQ7Sptyql3nb3Up7iaR09XYhcdYVarDkwnmX4/O6XyY+x 0tEg== X-Gm-Message-State: AOAM530qn0oyAO4kbjErxZaw49wop+w2o/rrQIc73UobgEb9AU5wpcwS wl6VuOQiek3dlgB+Tw+d39S/2Q== X-Google-Smtp-Source: ABdhPJyPQg1FpZjcUx+RNaSk3Z0uB0vB4JXzkK2pjJD8AjXfQL76MIafNbVdr3ZrCY8bDGXBAwq3dg== X-Received: by 2002:aca:4142:: with SMTP id o63mr4085367oia.167.1600825436078; Tue, 22 Sep 2020 18:43:56 -0700 (PDT) Received: from shuah-t480s.internal (c-24-9-64-241.hsd1.co.comcast.net. [24.9.64.241]) by smtp.gmail.com with ESMTPSA id y23sm8801820ooj.34.2020.09.22.18.43.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Sep 2020 18:43:55 -0700 (PDT) From: Shuah Khan To: corbet@lwn.net, keescook@chromium.org, gregkh@linuxfoundation.org, shuah@kernel.org, rafael@kernel.org, johannes@sipsolutions.net, lenb@kernel.org, james.morse@arm.com, tony.luck@intel.com, bp@alien8.de, arve@android.com, tkjos@android.com, maco@android.com, joel@joelfernandes.org, christian@brauner.io, hridya@google.com, surenb@google.com, minyard@acm.org, arnd@arndb.de, mchehab@kernel.org, rric@kernel.org Cc: Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-acpi@vger.kernel.org, devel@driverdev.osuosl.org, openipmi-developer@lists.sourceforge.net, linux-edac@vger.kernel.org Subject: [RFC PATCH 00/11] Introduce Simple atomic and non-atomic counters Date: Tue, 22 Sep 2020 19:43:29 -0600 Message-Id: X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org This patch series is a result of discussion at the refcount_t BOF the Linux Plumbers Conference. In this discussion, we identifed a need for looking closely and investigating atomic_t usages in the kernel when it is used strictly as a counter wothout it controlling object lifetimes and state changes. There are a number of atomic_t usages in the kernel where atomic_t api is used strictly for counting and not for managing object lifetime. In some cases, atomic_t might not even be needed. The purpose of these counters is twofold: 1. clearly differentiate atomic_t counters from atomic_t usages that guard object lifetimes, hence prone to overflow and underflow errors. It allows tools that scan for underflow and overflow on atomic_t usages to detect overflow and underflows to scan just the cases that are prone to errors. 2. provides non-atomic counters for cases where atomic isn't necessary. Simple atomic and non-atomic counters api provides interfaces for simple atomic and non-atomic counters that just count, and don't guard resource lifetimes. Counters will wrap around to 0 when it overflows and should not be used to guard resource lifetimes, device usage and open counts that control state changes, and pm states. Using counter_atomic to guard lifetimes could lead to use-after free when it overflows and undefined behavior when used to manage state changes and device usage/open states. This patch series introduces Simple atomic and non-atomic counters. Counter atomic ops leverage atomic_t and provide a sub-set of atomic_t ops. In addition this patch series converts a few drivers to use the new api. The following criteria is used for select variables for conversion: 1. Variable doesn't guard object lifetimes, manage state changes e.g: device usage counts, device open counts, and pm states. 2. Variable is used for stats and counters. 3. The conversion doesn't change the overflow behavior. Please review and let me know if non-stat conversions e.g: probe_count, deferred_trigger_count make sense. Shuah Khan (11): counters: Introduce counter and counter_atomic counters selftests:lib:test_counters: add new test for counters drivers/base: convert deferred_trigger_count and probe_count to counter_atomic drivers/base/devcoredump: convert devcd_count to counter_atomic drivers/acpi: convert seqno counter_atomic drivers/acpi/apei: convert seqno counter_atomic drivers/android/binder: convert stats, transaction_log to counter_atomic drivers/base/test/test_async_driver_probe: convert to use counter_atomic drivers/char/ipmi: convert stats to use counter_atomic drivers/misc/vmw_vmci: convert num guest devices counter to counter_atomic drivers/edac: convert pci counters to counter_atomic Documentation/core-api/counters.rst | 158 +++++++++ MAINTAINERS | 8 + drivers/acpi/acpi_extlog.c | 5 +- drivers/acpi/apei/ghes.c | 5 +- drivers/android/binder.c | 41 +-- drivers/android/binder_internal.h | 3 +- drivers/base/dd.c | 19 +- drivers/base/devcoredump.c | 5 +- drivers/base/test/test_async_driver_probe.c | 23 +- drivers/char/ipmi/ipmi_msghandler.c | 9 +- drivers/char/ipmi/ipmi_si_intf.c | 9 +- drivers/edac/edac_pci.h | 5 +- drivers/edac/edac_pci_sysfs.c | 28 +- drivers/misc/vmw_vmci/vmci_guest.c | 9 +- include/linux/counters.h | 343 +++++++++++++++++++ lib/Kconfig | 10 + lib/Makefile | 1 + lib/test_counters.c | 283 +++++++++++++++ tools/testing/selftests/lib/Makefile | 1 + tools/testing/selftests/lib/config | 1 + tools/testing/selftests/lib/test_counters.sh | 5 + 21 files changed, 897 insertions(+), 74 deletions(-) create mode 100644 Documentation/core-api/counters.rst create mode 100644 include/linux/counters.h create mode 100644 lib/test_counters.c create mode 100755 tools/testing/selftests/lib/test_counters.sh -- 2.25.1