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[24.9.64.241]) by smtp.gmail.com with ESMTPSA id h21sm399684iob.30.2021.02.03.10.12.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 10:12:12 -0800 (PST) From: Shuah Khan To: corbet@lwn.net, gregkh@linuxfoundation.org, peterz@infradead.org, keescook@chromium.org, rafael@kernel.org, lenb@kernel.org, james.morse@arm.com, tony.luck@intel.com, bp@alien8.de Cc: Shuah Khan , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, devel@driverdev.osuosl.org Subject: [PATCH v3 1/7] seqnum_ops: Introduce Sequence Number Ops Date: Wed, 3 Feb 2021 11:11:57 -0700 Message-Id: <23f6347a7bb9f902babe7351f71b23644035673d.1612314468.git.skhan@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Sequence Number api provides interfaces for unsigned atomic up counters. 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. Sequence Number ops provide interfaces to initialize, increment and get the sequence number. These ops also check for overflow and log message to indicate when overflow occurs. Signed-off-by: Shuah Khan --- Documentation/core-api/index.rst | 1 + Documentation/core-api/seqnum_ops.rst | 53 ++++++++++ MAINTAINERS | 7 ++ include/linux/seqnum_ops.h | 129 +++++++++++++++++++++++++ lib/Kconfig | 9 ++ lib/Makefile | 1 + lib/test_seqnum_ops.c | 133 ++++++++++++++++++++++++++ 7 files changed, 333 insertions(+) create mode 100644 Documentation/core-api/seqnum_ops.rst create mode 100644 include/linux/seqnum_ops.h create mode 100644 lib/test_seqnum_ops.c diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index f1c9d20bd42d..adc8b1ae2acf 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -54,6 +54,7 @@ How Linux keeps everything from happening at the same time. See :maxdepth: 1 refcount-vs-atomic + seqnum_ops irq/index local_ops padata diff --git a/Documentation/core-api/seqnum_ops.rst b/Documentation/core-api/seqnum_ops.rst new file mode 100644 index 000000000000..ed4eba394799 --- /dev/null +++ b/Documentation/core-api/seqnum_ops.rst @@ -0,0 +1,53 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: + +.. _seqnum_ops: + +========================== +Sequence Number Operations +========================== + +:Author: Shuah Khan +:Copyright: |copy| 2021, The Linux Foundation +:Copyright: |copy| 2021, Shuah Khan + +Sequence Number api provides interfaces for unsigned up counters. + +Sequence Number Ops +=================== + +seqnum32 and seqnum64 types support implementing unsigned up counters. :: + + struct seqnum32 { u32 seqnum; }; + struct seqnum64 { u64 seqnum; }; + +Initializers +------------ + +Interfaces for initializing sequence numbers. :: + + #define SEQNUM_INIT(i) { .seqnum = i } + seqnum32_init(seqnum, val) + seqnum64_init(seqnum, val) + +Increment interface +------------------- + +Increments sequence number and returns the new value. Checks for overflow +conditions and logs message when overflow occurs. This check is intended +to help catch cases where overflow could lead to problems. :: + + seqnum32_inc(seqnum): Calls atomic_inc_return(seqnum). + seqnum64_inc(seqnum): Calls atomic64_inc_return(seqnum). + +Return/get value interface +-------------------------- + +Returns sequence number value. :: + + seqnum32_get() - return seqnum value. + seqnum64_get() - return seqnum value. + +.. warning:: + seqnum32 wraps around to INT_MIN when it overflows. diff --git a/MAINTAINERS b/MAINTAINERS index cc1e6a5ee6e6..f9fe1438a8cd 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -16235,6 +16235,13 @@ S: Maintained F: Documentation/fb/sm712fb.rst F: drivers/video/fbdev/sm712* +SEQNUM OPS +M: Shuah Khan +L: linux-kernel@vger.kernel.org +S: Maintained +F: include/linux/seqnum_ops.h +F: lib/test_seqnum_ops.c + SIMPLE FIRMWARE INTERFACE (SFI) S: Obsolete W: http://simplefirmware.org/ diff --git a/include/linux/seqnum_ops.h b/include/linux/seqnum_ops.h new file mode 100644 index 000000000000..e8d8481445d3 --- /dev/null +++ b/include/linux/seqnum_ops.h @@ -0,0 +1,129 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * seqnum_ops.h - Interfaces for unsigned atomic sequential up counters. + * + * Copyright (c) 2021 Shuah Khan + * Copyright (c) 2021 The Linux Foundation + * + * Sequence Number functions provide support for unsgined atomic up + * counters. + * + * The interface provides: + * seqnumu32 & seqnumu64 functions: + * initialization + * increment and return + * + * seqnumu32 and seqnumu64 functions leverage/use atomic*_t ops to + * implement support for unsigned atomic up counters. + * + * Reference and API guide: + * Documentation/core-api/seqnum_ops.rst for more information. + */ + +#ifndef __LINUX_SEQNUM_OPS_H +#define __LINUX_SEQNUM_OPS_H + +#include + +/** + * struct seqnum32 - Sequence number atomic counter + * @seqnum: atomic_t + * + **/ +struct seqnum32 { + u32 seqnum; +}; + +#define SEQNUM_INIT(i) { .seqnum = i } + +/* + * seqnum32_init() - initialize seqnum value + * @seq: struct seqnum32 pointer + * + */ +static inline void seqnum32_init(struct seqnum32 *seq, u32 val) +{ + seq->seqnum = val; +} + +/* + * seqnum32_inc() - increment seqnum value and return the new value + * @seq: struct seqnum32 pointer + * + * Return u32 + */ +static inline u32 seqnum32_inc(struct seqnum32 *seq) +{ + atomic_t val = ATOMIC_INIT(seq->seqnum); + + seq->seqnum = (u32) atomic_inc_return(&val); + if (seq->seqnum >= UINT_MAX) + pr_info("Sequence Number overflow %u detected\n", + seq->seqnum); + return seq->seqnum; +} + +/* + * seqnum32_get() - get seqnum value + * @seq: struct seqnum32 pointer + * + * Return u32 + */ +static inline u32 seqnum32_get(struct seqnum32 *seq) +{ + return seq->seqnum; +} + +/* + * struct seqnum64 - Sequential/Statistical atomic counter + * @seq: atomic64_t + * + */ +struct seqnum64 { + u64 seqnum; +}; + +/* Add to a global include/vdso/limits.h and fix all other UINT64_MAX + * duplicate defines? + */ +#define SEQ_UINT64_MAX ((u64)(~((u64) 0))) /* 0xFFFFFFFFFFFFFFFF */ + +/* + * seqnum64_init() - initialize seqnum value + * @seq: struct seqnum64 pointer + * + */ +static inline void seqnum64_init(struct seqnum64 *seq, u64 val) +{ + seq->seqnum = val; +} + +/* + * seqnum64_inc() - increment seqnum value and return the new value + * @seq: struct seqnum64 pointer + * + * Return u64 + */ +static inline u64 seqnum64_inc(struct seqnum64 *seq) +{ + atomic64_t val = ATOMIC_INIT(seq->seqnum); + + seq->seqnum = (u64) atomic64_inc_return(&val); + if (seq->seqnum >= SEQ_UINT64_MAX) + pr_info("Sequence Number overflow %llu detected\n", + seq->seqnum); + return seq->seqnum; +} + +/* + * seqnum64_get() - get seqnum value + * @seq: struct seqnum64 pointer + * + * Return u64 + */ +static inline u64 seqnum64_get(struct seqnum64 *seq) +{ + return (u64) seq->seqnum; +} + +#endif /* __LINUX_SEQNUM_OPS_H */ diff --git a/lib/Kconfig b/lib/Kconfig index 46806332a8cc..518de7d34606 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -663,6 +663,15 @@ config OBJAGG config STRING_SELFTEST tristate "Test string functions" +config TEST_SEQNUM_OPS + tristate "Test Sequence Number Ops API" + help + A test module for Sequence Number Ops API. A corresponding + selftest can be used to test the Seqnum Ops API. Select this + for testing Sequence Number Ops API. + + See Documentation/core-api/seqnum_ops.rst + endmenu config GENERIC_IOREMAP diff --git a/lib/Makefile b/lib/Makefile index afeff05fa8c5..917686063cb3 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -101,6 +101,7 @@ obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o obj-$(CONFIG_TEST_LOCKUP) += test_lockup.o obj-$(CONFIG_TEST_HMM) += test_hmm.o obj-$(CONFIG_TEST_FREE_PAGES) += test_free_pages.o +obj-$(CONFIG_TEST_SEQNUM_OPS) += test_seqnum_ops.o # # CFLAGS for compiling floating point code inside the kernel. x86/Makefile turns diff --git a/lib/test_seqnum_ops.c b/lib/test_seqnum_ops.c new file mode 100644 index 000000000000..173278314f26 --- /dev/null +++ b/lib/test_seqnum_ops.c @@ -0,0 +1,133 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * test_seqnum_ops.c - Kernel module for testing Seqnum API + * + * Copyright (c) 2021 Shuah Khan + * Copyright (c) 2021 The Linux Foundation + * + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include + +static inline void +test_seqnum32_result(char *msg, u32 start, u32 end, u32 expected) +{ + pr_info("%s: %u to %u - %s\n", + msg, start, end, + ((expected == end) ? "PASS" : "FAIL")); +} + + +static void test_seqnum32(void) +{ + u32 start_val = 0; + struct seqnum32 seq = SEQNUM_INIT(start_val); + u32 end_val; + + end_val = seqnum32_inc(&seq); + test_seqnum32_result("Test increment", + start_val, end_val, start_val+1); + + /* Initialize sequence number to 0 */ + seqnum32_init(&seq, 0); + end_val = seqnum32_inc(&seq); + /* If seqnum32_init() works correctly end_val should be 1 */ + test_seqnum32_result("Test init", start_val, end_val, 1); + + /* seqnum32_get() test for seqnum value == 1 */ + start_val = end_val = seqnum32_get(&seq); + test_seqnum32_result("Test get", start_val, end_val, 1); +} + +static void test_seqnum32_overflow(u32 val) +{ + u32 start_val; + struct seqnum32 seq; + u32 end_val; + + pr_info("Test with start_val UINT_MAX-1 + %u\n", val); + start_val = UINT_MAX-1 + val; + seqnum32_init(&seq, start_val); + end_val = seqnum32_inc(&seq); + test_seqnum32_result("Test UINT_MAX limit compare with (val+1)", + start_val, end_val, start_val+1); + test_seqnum32_result("Test UINT_MAX limit compare with (UINT_MAX)", + start_val, end_val, UINT_MAX+val); +} + +static inline void +test_seqnum64_result(char *msg, u64 start, u64 end, u64 expected) +{ + pr_info("%s: %llu to %llu - %s\n", + msg, start, end, + ((expected == end) ? "PASS" : "FAIL")); +} + +static void test_seqnum64(void) +{ + u64 start_val = 0; + struct seqnum64 seq = SEQNUM_INIT(start_val); + u64 end_val; + + end_val = seqnum64_inc(&seq); + test_seqnum64_result("Test increment", + start_val, end_val, start_val+1); + + /* Initialize sequence number to 0 */ + seqnum64_init(&seq, start_val); + end_val = seqnum64_inc(&seq); + + /* if seqnum642_init() works correctly end_val should be 1 */ + test_seqnum64_result("Test init", start_val, end_val, 1); + /* seqnum64_get() test for seqnum value == 1 */ + start_val = end_val = seqnum64_get(&seq); + test_seqnum64_result("Test get", start_val, end_val, 1); +} + +static void test_seqnum64_overflow(u64 val) +{ + u64 start_val; + struct seqnum64 seq; + u64 end_val; + + pr_info("Test with start_val SEQ_UINT64_MAX-1 + %llu\n", val); + start_val = SEQ_UINT64_MAX-1 + val; + seqnum64_init(&seq, start_val); + end_val = seqnum64_inc(&seq); + test_seqnum64_result("Test UINT64_MAX limit compare with (val+1)", + start_val, end_val, start_val+1); + test_seqnum64_result("Test UINT64_MAX limit compare with (UINT64_MAX)", + start_val, end_val, SEQ_UINT64_MAX+val); +} + +static int __init test_seqnum_ops_init(void) +{ + pr_info("Start seqnum32_*() interfaces test\n"); + test_seqnum32(); + test_seqnum32_overflow(0); + test_seqnum32_overflow(5); + pr_info("End seqnum32_*() interfaces test\n\n"); + + pr_info("Start seqnum64_*() interfaces test\n"); + test_seqnum64(); + test_seqnum64_overflow(0); + test_seqnum64_overflow(5); + pr_info("End seqnum64_*() interfaces test\n\n"); + + return 0; +} + +module_init(test_seqnum_ops_init); + +static void __exit test_seqnum_ops_exit(void) +{ + pr_info("exiting.\n"); +} + +module_exit(test_seqnum_ops_exit); + +MODULE_AUTHOR("Shuah Khan "); +MODULE_LICENSE("GPL v2");