From patchwork Thu Jan 11 21:24:22 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Matthew Wilcox (Oracle)" X-Patchwork-Id: 13517790 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0B08758212; Thu, 11 Jan 2024 21:24:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ugXSvcPb" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=h5JRxZmfjqOYZZRAvRI1Cwt+9QteJXdUxDRr8ebrX5I=; b=ugXSvcPbPDTMiiIY8MjQ/FEQyf j3wIORkZgDASPDZrAeyTJLPHae7YoeOIPuXQyz6T5xwxRYQtGLRwZ2NBqCXHF68rdTNgK2JkKql8l YBFtQth0SXlGA9tmI70yaZFUQgfnP3+14C7BBj308g2XbFt7WiB1p1yC2yuqhP3oME15RRmYhtv6d 6NgmlogEx64E4Ko4vVH1K5NMudBEFM+Rxk0tpcYYfHVlHPu/tWeFGSpWYQ7hj+r4CVwDMiSw7ggH8 Q6w5Bts9mCAUtcZbKTped29C/6bd/5Tc4tusZCcKya6iBPfYfCIcOdJ/yv4H0wniW59TUJy40ar90 F175KuYw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1rO2XO-00EzIG-Go; Thu, 11 Jan 2024 21:24:30 +0000 From: "Matthew Wilcox (Oracle)" To: Chandan Babu R Cc: "Matthew Wilcox (Oracle)" , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, "Darrick J . Wong" , Mateusz Guzik , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long Subject: [PATCH v5 1/3] locking: Add rwsem_assert_held() and rwsem_assert_held_write() Date: Thu, 11 Jan 2024 21:24:22 +0000 Message-Id: <20240111212424.3572189-2-willy@infradead.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20240111212424.3572189-1-willy@infradead.org> References: <20240111212424.3572189-1-willy@infradead.org> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Modelled after lockdep_assert_held() and lockdep_assert_held_write(), but are always active, even when lockdep is disabled. Of course, they don't test that _this_ thread is the owner, but it's sufficient to catch many bugs and doesn't incur the same performance penalty as lockdep. Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Peter Zijlstra (Intel) Acked-by: Waiman Long Acked-by: Darrick J. Wong --- include/linux/rwbase_rt.h | 9 ++++++-- include/linux/rwsem.h | 46 ++++++++++++++++++++++++++++++++++----- 2 files changed, 48 insertions(+), 7 deletions(-) diff --git a/include/linux/rwbase_rt.h b/include/linux/rwbase_rt.h index 1d264dd08625..29c4e4f243e4 100644 --- a/include/linux/rwbase_rt.h +++ b/include/linux/rwbase_rt.h @@ -26,12 +26,17 @@ struct rwbase_rt { } while (0) -static __always_inline bool rw_base_is_locked(struct rwbase_rt *rwb) +static __always_inline bool rw_base_is_locked(const struct rwbase_rt *rwb) { return atomic_read(&rwb->readers) != READER_BIAS; } -static __always_inline bool rw_base_is_contended(struct rwbase_rt *rwb) +static inline void rw_base_assert_held_write(const struct rwbase_rt *rwb) +{ + WARN_ON(atomic_read(&rwb->readers) != WRITER_BIAS); +} + +static __always_inline bool rw_base_is_contended(const struct rwbase_rt *rwb) { return atomic_read(&rwb->readers) > 0; } diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 9c29689ff505..4f1c18992f76 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -66,14 +66,24 @@ struct rw_semaphore { #endif }; -/* In all implementations count != 0 means locked */ +#define RWSEM_UNLOCKED_VALUE 0UL +#define RWSEM_WRITER_LOCKED (1UL << 0) +#define __RWSEM_COUNT_INIT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE) + static inline int rwsem_is_locked(struct rw_semaphore *sem) { - return atomic_long_read(&sem->count) != 0; + return atomic_long_read(&sem->count) != RWSEM_UNLOCKED_VALUE; } -#define RWSEM_UNLOCKED_VALUE 0L -#define __RWSEM_COUNT_INIT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE) +static inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem) +{ + WARN_ON(atomic_long_read(&sem->count) == RWSEM_UNLOCKED_VALUE); +} + +static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem) +{ + WARN_ON(!(atomic_long_read(&sem->count) & RWSEM_WRITER_LOCKED)); +} /* Common initializer macros and functions */ @@ -152,11 +162,21 @@ do { \ __init_rwsem((sem), #sem, &__key); \ } while (0) -static __always_inline int rwsem_is_locked(struct rw_semaphore *sem) +static __always_inline int rwsem_is_locked(const struct rw_semaphore *sem) { return rw_base_is_locked(&sem->rwbase); } +static inline void rwsem_assert_held_nolockdep(const struct rw_semaphore *sem) +{ + WARN_ON(!rwsem_is_locked(sem)); +} + +static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem) +{ + rw_base_assert_held_write(sem); +} + static __always_inline int rwsem_is_contended(struct rw_semaphore *sem) { return rw_base_is_contended(&sem->rwbase); @@ -169,6 +189,22 @@ static __always_inline int rwsem_is_contended(struct rw_semaphore *sem) * the RT specific variant. */ +static inline void rwsem_assert_held(const struct rw_semaphore *sem) +{ + if (IS_ENABLED(CONFIG_LOCKDEP)) + lockdep_assert_held(sem); + else + rwsem_assert_held_nolockdep(sem); +} + +static inline void rwsem_assert_held_write(const struct rw_semaphore *sem) +{ + if (IS_ENABLED(CONFIG_LOCKDEP)) + lockdep_assert_held_write(sem); + else + rwsem_assert_held_write_nolockdep(sem); +} + /* * lock for reading */