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=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 3957EC433FE for ; Mon, 7 Dec 2020 15:58:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A205923731 for ; Mon, 7 Dec 2020 15:58:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727358AbgLGP54 (ORCPT ); Mon, 7 Dec 2020 10:57:56 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:50440 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726167AbgLGP54 (ORCPT ); Mon, 7 Dec 2020 10:57:56 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1kmIsy-00EPxe-Ho; Mon, 07 Dec 2020 08:57:12 -0700 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1kmIsx-0007O9-BU; Mon, 07 Dec 2020 08:57:12 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Peter Zijlstra Cc: Waiman Long , linux-kernel@vger.kernel.org, Linus Torvalds , Ingo Molnar , Will Deacon , Jann Horn , Vasiliy Kulikov , Al Viro , Bernd Edlinger , Oleg Nesterov , Christopher Yeoh , Cyrill Gorcunov , Sargun Dhillon , Christian Brauner , Arnd Bergmann , Arnaldo Carvalho de Melo References: <87tut2bqik.fsf@x220.int.ebiederm.org> <87k0tybqfy.fsf@x220.int.ebiederm.org> <620f0908-c70a-9e54-e1b5-71d086b20756@redhat.com> <20201207090243.GE3040@hirez.programming.kicks-ass.net> Date: Mon, 07 Dec 2020 09:56:34 -0600 In-Reply-To: <20201207090243.GE3040@hirez.programming.kicks-ass.net> (Peter Zijlstra's message of "Mon, 7 Dec 2020 10:02:43 +0100") Message-ID: <87360hy5hp.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1kmIsx-0007O9-BU;;;mid=<87360hy5hp.fsf@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/4Dv8ij08d6JmqqyY9GO2q9L+ifSbts+M= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 2/3] rwsem: Implement down_read_interruptible X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Thu, Dec 03, 2020 at 08:59:13PM -0500, Waiman Long wrote: >> On 12/3/20 3:11 PM, Eric W. Biederman wrote: > >> > +static inline int __down_read_interruptible(struct rw_semaphore *sem) >> > +{ >> > + if (!rwsem_read_trylock(sem)) { >> > + if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE))) >> > + return -EINTR; >> > + DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); >> > + } else { >> > + rwsem_set_reader_owned(sem); >> > + } >> > + return 0; >> > +} >> > + >> > static inline int __down_read_killable(struct rw_semaphore *sem) >> > { >> > if (!rwsem_read_trylock(sem)) { >> > @@ -1495,6 +1507,20 @@ void __sched down_read(struct rw_semaphore *sem) >> > } >> > EXPORT_SYMBOL(down_read); >> > +int __sched down_read_interruptible(struct rw_semaphore *sem) >> > +{ >> > + might_sleep(); >> > + rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); >> > + >> > + if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) { >> > + rwsem_release(&sem->dep_map, _RET_IP_); >> > + return -EINTR; >> > + } >> > + >> > + return 0; >> > +} >> > +EXPORT_SYMBOL(down_read_interruptible); >> > + >> > int __sched down_read_killable(struct rw_semaphore *sem) >> > { >> > might_sleep(); >> >> Acked-by: Waiman Long > > Yeah, that seems correct.. There's an unfortunate amount of copy-paste > there though. > > Do we want to follow that up with something like this? Do you want to pull these two into a topic branch in the tip tree based on v10-rc1? That way we can share these two patches, and then you folks can make your locking cleanups and I can change exec_update_mutex to a rw_semaphore? Eric > --- > --- a/kernel/locking/rwsem.c > +++ b/kernel/locking/rwsem.c > @@ -275,7 +275,25 @@ static inline bool rwsem_read_trylock(st > long cnt = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count); > if (WARN_ON_ONCE(cnt < 0)) > rwsem_set_nonspinnable(sem); > - return !(cnt & RWSEM_READ_FAILED_MASK); > + > + if (!(cnt & RWSEM_READ_FAILED_MASK)) { > + rwsem_set_reader_owned(sem); > + return true; > + } > + > + return false; > +} > + > +static inline bool rwsem_write_trylock(struct rw_semaphore *sem) > +{ > + long tmp = RWSEM_UNLOCKED_VALUE; > + > + if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, RWSEM_WRITER_LOCKED)) { > + rwsem_set_owner(sem); > + return true; > + } > + > + return false; > } > > /* > @@ -1335,38 +1353,29 @@ static struct rw_semaphore *rwsem_downgr > /* > * lock for reading > */ > -static inline void __down_read(struct rw_semaphore *sem) > +static inline int __down_read_common(struct rw_semaphore *sem, int state) > { > if (!rwsem_read_trylock(sem)) { > - rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE); > + if (IS_ERR(rwsem_down_read_slowpath(sem, state))) > + return -EINTR; > DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); > - } else { > - rwsem_set_reader_owned(sem); > } > + return 0; > } > > -static inline int __down_read_interruptible(struct rw_semaphore *sem) > +static __always_inline void __down_read(struct rw_semaphore *sem) > { > - if (!rwsem_read_trylock(sem)) { > - if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_INTERRUPTIBLE))) > - return -EINTR; > - DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); > - } else { > - rwsem_set_reader_owned(sem); > - } > - return 0; > + __down_read_common(sem, TASK_UNINTERRUPTIBLE); > } > > -static inline int __down_read_killable(struct rw_semaphore *sem) > +static __always_inline int __down_read_interruptible(struct rw_semaphore *sem) > { > - if (!rwsem_read_trylock(sem)) { > - if (IS_ERR(rwsem_down_read_slowpath(sem, TASK_KILLABLE))) > - return -EINTR; > - DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem); > - } else { > - rwsem_set_reader_owned(sem); > - } > - return 0; > + return __down_read_common(sem, TASK_INTERRUPTIBLE); > +} > + > +static __always_inline int __down_read_killable(struct rw_semaphore *sem) > +{ > + return __down_read_common(sem, TASK_KILLABLE); > } > > static inline int __down_read_trylock(struct rw_semaphore *sem) > @@ -1392,44 +1401,29 @@ static inline int __down_read_trylock(st > /* > * lock for writing > */ > -static inline void __down_write(struct rw_semaphore *sem) > +static inline int __down_write_common(struct rw_semaphore *sem, int state) > { > - long tmp = RWSEM_UNLOCKED_VALUE; > - > - if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, > - RWSEM_WRITER_LOCKED))) > - rwsem_down_write_slowpath(sem, TASK_UNINTERRUPTIBLE); > - else > - rwsem_set_owner(sem); > + if (unlikely(!rwsem_write_trylock(sem))) { > + if (IS_ERR(rwsem_down_write_slowpath(sem, state))) > + return -EINTR; > + } > + return 0; > } > > -static inline int __down_write_killable(struct rw_semaphore *sem) > +static __always_inline void __down_write(struct rw_semaphore *sem) > { > - long tmp = RWSEM_UNLOCKED_VALUE; > + __down_write_common(sem, TASK_UNINTERRUPTIBLE); > +} > > - if (unlikely(!atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, > - RWSEM_WRITER_LOCKED))) { > - if (IS_ERR(rwsem_down_write_slowpath(sem, TASK_KILLABLE))) > - return -EINTR; > - } else { > - rwsem_set_owner(sem); > - } > - return 0; > +static __always_inline int __down_write_killable(struct rw_semaphore *sem) > +{ > + return __down_write_common(sem, TASK_KILLABLE); > } > > static inline int __down_write_trylock(struct rw_semaphore *sem) > { > - long tmp; > - > DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem); > - > - tmp = RWSEM_UNLOCKED_VALUE; > - if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp, > - RWSEM_WRITER_LOCKED)) { > - rwsem_set_owner(sem); > - return true; > - } > - return false; > + return rwsem_write_trylock(sem); > } > > /*