@@ -78,3 +78,12 @@ Fetched and returns current sequence number value. ::
seqnum32_fetch() --> (u32) atomic_add_return(0, seqnum)
seqnum64_fetch() --> (u64) atomic64_add_return(0, seqnum)
+
+Where are the seqnum_ops and how to use and test them?
+------------------------------------------------------
+
+.. kernel-doc:: include/linux/seqnum_ops.h
+
+Please see lib/test_seqnum_ops.c for examples usages and test module.
+Please find selftest: testing/selftests/lib/test_seqnum_ops.sh
+Please check dmesg for results after running test_seqnum_ops.sh.
@@ -15983,6 +15983,7 @@ L: linux-kernel@vger.kernel.org
S: Maintained
F: include/linux/seqnum_ops.h
F: lib/test_seqnum_ops.c
+F: tools/testing/selftests/lib/test_seqnum_ops.sh
SIMPLE FIRMWARE INTERFACE (SFI)
S: Obsolete
@@ -19,6 +19,8 @@
*
* Reference and API guide:
* Documentation/core-api/seqnum_ops.rst for more information.
+ * lib/test_seqnum_ops.c - example usages and test module
+ * tools/testing/selftests/lib/test_seqnum_ops.sh
*/
#ifndef __LINUX_SEQNUM_OPS_H
@@ -5,5 +5,6 @@
all:
TEST_PROGS := printf.sh bitmap.sh prime_numbers.sh strscpy.sh
+TEST_PROGS += test_seqnum_ops.sh
include ../lib.mk
@@ -3,3 +3,4 @@ CONFIG_TEST_BITMAP=m
CONFIG_PRIME_NUMBERS=m
CONFIG_TEST_STRSCPY=m
CONFIG_TEST_BITOPS=m
+CONFIG_TEST_SEQNUM_OPS=m
new file mode 100755
@@ -0,0 +1,10 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (c) 2020 Shuah Khan <skhan@linuxfoundation.org>
+# Copyright (c) 2020 The Linux Foundation
+#
+# Tests the Sequence Number Ops interfaces using test_seqnum_ops
+# kernel module
+#
+$(dirname $0)/../kselftest/module.sh "test_seqnum_ops" test_seqnum_ops
Add a new selftest for testing seqnum_ops. This test loads test_seqnum_ops test module and unloads it. The test module runs tests and prints results to dmesg. Sequence Number api provides interfaces for unsigned atomic up counters leveraging atomic_t and atomic64_t ops underneath. There are a number of atomic_t usages in the kernel where atomic_t api is used for counting sequence numbers and other statistical counters. Several of these usages, convert atomic_read() and atomic_inc_return() return values to unsigned. Introducing sequence number ops supports these use-cases with a standard core-api. The atomic_t api provides a wide range of atomic operations as a base api to implement atomic counters, bitops, spinlock interfaces. The usages also evolved into being used for resource lifetimes and state management. The refcount_t api was introduced to address resource lifetime problems related to atomic_t wrapping. There is a large overlap between the atomic_t api used for resource lifetimes and just counters, stats, and sequence numbers. It has become difficult to differentiate between the atomic_t usages that should be converted to refcount_t and the ones that can be left alone. Introducing seqnum_ops to wrap the usages that are stats, counters, sequence numbers makes it easier for 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. In addition, to supporting sequence number use-cases, Sequence Number Ops helps differentiate atomic_t counter usages from atomic_t usages that guard object lifetimes, hence prone to overflow and underflow errors from up counting use-cases. Signed-off-by: Shuah Khan <skhan@linuxfoundation.org> --- Documentation/core-api/seqnum_ops.rst | 9 +++++++++ MAINTAINERS | 1 + include/linux/seqnum_ops.h | 2 ++ tools/testing/selftests/lib/Makefile | 1 + tools/testing/selftests/lib/config | 1 + tools/testing/selftests/lib/test_seqnum_ops.sh | 10 ++++++++++ 6 files changed, 24 insertions(+) create mode 100755 tools/testing/selftests/lib/test_seqnum_ops.sh