From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8EF8AA28; Sat, 13 Jan 2024 00:38:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="seVOur25" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC59FC43390; Sat, 13 Jan 2024 00:38:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1705106297; bh=/eeFF6/JtaBBkHTd6iYnBzPQb/6NBh8oA+UF/0yDTRk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=seVOur25lNIR/X3Cq31wwPlG6ywe+zK8wg4yPuMaL1cTEZXUcbnd+tqbqLEol7Wxp E3GLCl08xmNZu3iJ3CnGJP73ya57Nb90ZEj5wQ4gPX0ojmV9p7KIDNhBkUaC7KYkik 2923k8sJTcCmqm+lN7VqdrGVqDqHMvJNzYeDNVovP2Gv8H2e6/oeNPlzakAXuUY+Pn LBZpEhaGsee4aWqzYtaFSrWyAacKMM7bmrnYd5BzANsQ1+X5fepEGWkcbXMze+kF2B 3WyYGZ4EfnsUn34tA4LlH2190cdAF5qElUsR+fKvuy975c5FHH6vgUE6cAR7u8wj13 CITxHtTBcPqbQ== Date: Fri, 12 Jan 2024 16:38:16 -0800 From: "Darrick J. Wong" To: "Matthew Wilcox (Oracle)" Cc: Chandan Babu R , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, Mateusz Guzik , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long Subject: Re: [PATCH v5 1/3] locking: Add rwsem_assert_held() and rwsem_assert_held_write() Message-ID: <20240113003816.GB722975@frogsfrogsfrogs> References: <20240111212424.3572189-1-willy@infradead.org> <20240111212424.3572189-2-willy@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240111212424.3572189-2-willy@infradead.org> On Thu, Jan 11, 2024 at 09:24:22PM +0000, Matthew Wilcox (Oracle) wrote: > 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) Looks good to me, having read this patchset backwards. Acked-by: Darrick J. Wong --D > --- > 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 > */ > -- > 2.43.0 > >