From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 B9FE62C869 for ; Mon, 6 Nov 2023 19:11:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AEvpKN8q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1699297908; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NFYAlpr3mCFx2VdOux1+OiNwc+JRrHXIPRJP0tooHeo=; b=AEvpKN8qkhRtXdQ+3lW1bTQrYxSWCv799eE+UlSQzpVrU+nS69fvs+EI2lWaA2Ul3uviIv iYPHKCgFYzLaNlB0t4M1HTYX5uMtpVJbezH1xZiicycEBzvLuyEFJIZHWi8N08R0EvOqMM +CVizxy6ihjJnzdtWC639NfZd+wVyNA= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-347-oHThYmJUOn6oNy-3gimBAA-1; Mon, 06 Nov 2023 14:11:45 -0500 X-MC-Unique: oHThYmJUOn6oNy-3gimBAA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8E9072808FE6; Mon, 6 Nov 2023 19:11:44 +0000 (UTC) Received: from fs-i40c-03.fs.lab.eng.bos.redhat.com (fs-i40c-03.fast.rdu2.eng.redhat.com [10.6.23.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id 81CDF1121307; Mon, 6 Nov 2023 19:11:44 +0000 (UTC) From: Alexander Aring To: peterz@infradead.org Cc: will@kernel.org, gfs2@lists.linux.dev, aahringo@redhat.com, boqun.feng@gmail.com, mark.rutland@arm.com, linux-kernel@vger.kernel.org Subject: [PATCH 2/3] refcount: introduce __refcount_dec_and_lock macro Date: Mon, 6 Nov 2023 14:11:37 -0500 Message-Id: <20231106191138.3179599-2-aahringo@redhat.com> In-Reply-To: <20231106191138.3179599-1-aahringo@redhat.com> References: <20231106191138.3179599-1-aahringo@redhat.com> Precedence: bulk X-Mailing-List: gfs2@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 This patch adds the __refcount_dec_and_lock macro to generate code for a lock specific refcount_dec_and_lock implementation. Existing refcount_dec_and_lock implementation are updated to use the new __refcount_dec_and_lock macro. In future other lock implementation can added to use the refcount_dec_and_lock trick to only hold the lock when the refcount is going to be zero. Per subsystem own lock implementation can use the macro as well to provide such implementation for their own locking type. Co-developed: Peter Zijlstra Signed-off-by: Alexander Aring --- include/linux/refcount.h | 25 +++++++++++++++++++++++++ lib/refcount.c | 36 ++++++------------------------------ 2 files changed, 31 insertions(+), 30 deletions(-) diff --git a/include/linux/refcount.h b/include/linux/refcount.h index 741cc6295f54..d5cf40d3f4bc 100644 --- a/include/linux/refcount.h +++ b/include/linux/refcount.h @@ -362,6 +362,31 @@ static inline void refcount_dec(refcount_t *r) extern __must_check bool refcount_dec_if_one(refcount_t *r); extern __must_check bool refcount_dec_not_one(refcount_t *r); +/** + * __refcount_dec_and_lock - macro to create code to holding a lock if being + * able to decremnt refcount to 0 + * @_ref: the refcount + * @_lock: lock function call code + * @_unlock: unlock function call code + * + * The result will be directly returned as a right operand operation. Uusally + * the caller use it directly after a return statement. + */ +#define __refcount_dec_and_lock(_ref, _lock, _unlock) \ +({ \ + bool _ret = false; \ + \ + if (!refcount_dec_not_one(_ref)) { \ + _lock; \ + if (!refcount_dec_and_test(_ref)) \ + _unlock; \ + else \ + _ret = true; \ + } \ + \ + _ret; \ +}) + /** * refcount_dec_and_mutex_lock - return holding mutex if able to decrement * refcount to 0 diff --git a/lib/refcount.c b/lib/refcount.c index c37edf66994f..5511498df708 100644 --- a/lib/refcount.c +++ b/lib/refcount.c @@ -96,46 +96,22 @@ EXPORT_SYMBOL(refcount_dec_not_one); bool refcount_dec_and_mutex_lock(refcount_t *r, struct mutex *lock) { - if (refcount_dec_not_one(r)) - return false; - - mutex_lock(lock); - if (!refcount_dec_and_test(r)) { - mutex_unlock(lock); - return false; - } - - return true; + return __refcount_dec_and_lock(r, mutex_lock(lock), + mutex_unlock(lock)); } EXPORT_SYMBOL(refcount_dec_and_mutex_lock); bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock) { - if (refcount_dec_not_one(r)) - return false; - - spin_lock(lock); - if (!refcount_dec_and_test(r)) { - spin_unlock(lock); - return false; - } - - return true; + return __refcount_dec_and_lock(r, spin_lock(lock), + spin_unlock(lock)); } EXPORT_SYMBOL(refcount_dec_and_lock); bool refcount_dec_and_lock_irqsave(refcount_t *r, spinlock_t *lock, unsigned long *flags) { - if (refcount_dec_not_one(r)) - return false; - - spin_lock_irqsave(lock, *flags); - if (!refcount_dec_and_test(r)) { - spin_unlock_irqrestore(lock, *flags); - return false; - } - - return true; + return __refcount_dec_and_lock(r, spin_lock_irqsave(lock, *flags), + spin_unlock_irqrestore(lock, *flags)); } EXPORT_SYMBOL(refcount_dec_and_lock_irqsave); -- 2.39.3