From patchwork Mon Aug 29 12:47:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marco Elver X-Patchwork-Id: 12957760 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2118ECAAD5 for ; Mon, 29 Aug 2022 12:57:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229572AbiH2M5e (ORCPT ); Mon, 29 Aug 2022 08:57:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229880AbiH2M4c (ORCPT ); Mon, 29 Aug 2022 08:56:32 -0400 Received: from mail-ej1-x64a.google.com (mail-ej1-x64a.google.com [IPv6:2a00:1450:4864:20::64a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 39386D103 for ; Mon, 29 Aug 2022 05:48:27 -0700 (PDT) Received: by mail-ej1-x64a.google.com with SMTP id sg35-20020a170907a42300b007414343814bso1482554ejc.18 for ; Mon, 29 Aug 2022 05:48:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc; bh=o7nFvD+bAzzd8hTxdy6J5SFI8QAvwQGuiGUQWboy0hk=; b=DUROuHk1Z9qzwl+b2DTEg2S7HJMexhpmqANb/PJZ7O33R9XhSPct7AwehP14PQc/2o wK/bi8a2CwUsCNYLZ60BVrbEBT9p31oxiK+AfnIEOciyJytERkocF14TQxcpALfKW3+m b2Ub+eMgVCVEVNppFz86zBqIyKvR0lUxlYrSs0Pqqu53c88/O9WnN5AbglZY4E2lNY3X UurK/UKzohtpKpt81PvQ4NXYcynS9qosWESRGDtGbt4p3CdpxU/ZwTvmCC71hiCrb5Iz oBnMf/JVbgAxkVDKJuMfwanruY91nDmZy+mUGQ78tN/tN+0RJuWqqSZWWdmcn4+YhWS4 IZ8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc; bh=o7nFvD+bAzzd8hTxdy6J5SFI8QAvwQGuiGUQWboy0hk=; b=TzxrHSDb9wJaEfIaAKu1mn8AiAOwJMdCV9RKYg6HcLFdobRl8OeddMQIzdnJh3Perg B5+9jBrw1UtXHZ0hb/w16gsIBqPNcTN1x+R2batzgBvaqQaFZHralVXGwyi3KKZnm87z S4y2SHG3kdKuPtdek4kEbkqNMauejLIJB5fLKHHc/3rQo5Ir+D7Ix9OkJQTBlivZStUV 7kOBpVDDVxO6/VLUOnid1U+1e6EUTZZDd1LweTqFo3okADBR9kpKNffzxLBO7uK/ozo+ kOGiWRmDBOlHsm0HAAnXEsSRmhCD8bSRq2OdgaP/iWOczSPI0WKBGdoEPwftxs7zDswV V2vg== X-Gm-Message-State: ACgBeo1vbVWUaoaZYxf7V/yTwrwR7JUvfAw1B5hukUhrr7pRISiJuUl1 8Ft5mQ+KpQGJ80xBNkYcvdMdWwmksA== X-Google-Smtp-Source: AA6agR5wokwGhbG/dPuolBfo3Bpkl9cRXVj3x5ekleyIMoAvz+i6ptf2ezpCAANeuPi0p5VgMRtvOQZZzA== X-Received: from elver.muc.corp.google.com ([2a00:79e0:9c:201:196d:4fc7:fa9c:62e3]) (user=elver job=sendgmr) by 2002:a17:907:75c6:b0:741:75a0:b82b with SMTP id jl6-20020a17090775c600b0074175a0b82bmr4672915ejc.465.1661777305817; Mon, 29 Aug 2022 05:48:25 -0700 (PDT) Date: Mon, 29 Aug 2022 14:47:15 +0200 In-Reply-To: <20220829124719.675715-1-elver@google.com> Mime-Version: 1.0 References: <20220829124719.675715-1-elver@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220829124719.675715-11-elver@google.com> Subject: [PATCH v4 10/14] locking/percpu-rwsem: Add percpu_is_write_locked() and percpu_is_read_locked() From: Marco Elver To: elver@google.com, Peter Zijlstra , Frederic Weisbecker , Ingo Molnar Cc: Thomas Gleixner , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Dmitry Vyukov , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org, x86@kernel.org, linux-sh@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, Ian Rogers Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org Implement simple accessors to probe percpu-rwsem's locked state: percpu_is_write_locked(), percpu_is_read_locked(). Signed-off-by: Marco Elver Reviewed-by: Dmitry Vyukov Acked-by: Ian Rogers --- v4: * Due to spurious read_count increments in __percpu_down_read_trylock() if sem->block != 0, check that !sem->block (reported by Peter). v2: * New patch. --- include/linux/percpu-rwsem.h | 6 ++++++ kernel/locking/percpu-rwsem.c | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 5fda40f97fe9..36b942b67b7d 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -121,9 +121,15 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem) preempt_enable(); } +extern bool percpu_is_read_locked(struct percpu_rw_semaphore *); extern void percpu_down_write(struct percpu_rw_semaphore *); extern void percpu_up_write(struct percpu_rw_semaphore *); +static inline bool percpu_is_write_locked(struct percpu_rw_semaphore *sem) +{ + return atomic_read(&sem->block); +} + extern int __percpu_init_rwsem(struct percpu_rw_semaphore *, const char *, struct lock_class_key *); diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 5fe4c5495ba3..185bd1c906b0 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -192,6 +192,12 @@ EXPORT_SYMBOL_GPL(__percpu_down_read); __sum; \ }) +bool percpu_is_read_locked(struct percpu_rw_semaphore *sem) +{ + return per_cpu_sum(*sem->read_count) != 0 && !atomic_read(&sem->block); +} +EXPORT_SYMBOL_GPL(percpu_is_read_locked); + /* * Return true if the modular sum of the sem->read_count per-CPU variable is * zero. If this sum is zero, then it is stable due to the fact that if any