From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from unimail.uni-dortmund.de (mx1.hrz.uni-dortmund.de [129.217.128.51]) (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 B78173C3F41; Thu, 30 Jul 2026 21:40:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=129.217.128.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785447624; cv=none; b=uR50W/N60O4uZ6SIikxDxTlE+R7n6ntfIRWfUFvC8Wi4/3YRaGEHgUN8+5/Qi9rQ67Z1malRvMVPY/phiaSaModvwpMs8jNI2zKrp8aL0buLjUbwDhY0UBvvr1FFl4NwHEXKWddCQO/Mr/NykCROI5eW0Os+GQoGE1jnFbouRzA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785447624; c=relaxed/simple; bh=tCPRMEp6TmqL/fEFXU0YKQmIgtuzrv2hlx3vg5nK+a4=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=S7yjtV2pWhiie9GbWzPEv0qldLyL9uv44i2a864JCxOtCRJ1hsv/tRPIDfm2vNLtklX4Qk8DERSFFdfTYus+EPggSH1/M5gmgJAK+UaryXTjfQe4skIn7blvgHKKGSDz0YyIciICB0qBNWuOk1rDObA1+rH/YDd1vVCZYTRiobM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=tu-dortmund.de; spf=pass smtp.mailfrom=tu-dortmund.de; dkim=pass (1024-bit key) header.d=tu-dortmund.de header.i=@tu-dortmund.de header.b=UQG2ONSF; arc=none smtp.client-ip=129.217.128.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=tu-dortmund.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tu-dortmund.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=tu-dortmund.de header.i=@tu-dortmund.de header.b="UQG2ONSF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tu-dortmund.de; s=unimail; t=1785447415; bh=yR/DxJ9LQYfVsHAzHf/3wyLzlqaYWrGGsF3NNDyp3Aw=; h=From:To:Subject:Date:In-Reply-To:References; b=UQG2ONSFgAbPPkqYc+CZPWjDoR+YGSeugxCYnlsUrSYd3uGUo72myFJhYEcoC9N9U XwqIJ88+aDMIodhrtdT+5T/IWhO/spUaPBbV3Au09jdEz8sygCfCX8roh5P3heir8Z 8/VrQTFHpiFnNumkuLwKrY7mROFYmd52qjHIkAOg= Received: from simon-Latitude-5450.fritz.box (pd9eaa9cd.dip0.t-ipconnect.de [217.234.169.205]) (authenticated bits=0) by unimail.uni-dortmund.de (8.19.0.2/8.19.0.2) with ESMTPSA id 66ULan2w027704 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 30 Jul 2026 23:36:55 +0200 (CEST) From: Simon Schippers To: willemdebruijn.kernel@gmail.com, jasowangio@gmail.com, jasowang@redhat.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, mst@redhat.com, eperezma@redhat.com, leiyang@redhat.com, stephen@networkplumber.org, jon@nutanix.com, brett@librecast.net, corbet@lwn.net, skhan@linuxfoundation.org, tim.gebauer@tu-dortmund.de, simon.schippers@tu-dortmund.de, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux.dev Subject: [PATCH net-next v13 4/5] ptr_ring: move free-space check into separate helper Date: Thu, 30 Jul 2026 23:36:38 +0200 Message-ID: <20260730213639.726381-5-simon.schippers@tu-dortmund.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260730213639.726381-1-simon.schippers@tu-dortmund.de> References: <20260730213639.726381-1-simon.schippers@tu-dortmund.de> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This patch moves the check for available free space for a new entry into a separate function. Existing callers that only check for a non-zero return value are unaffected; __ptr_ring_produce() now returns -EINVAL for a zero-size ring and -ENOSPC when full, whereas before both cases returned -ENOSPC. The new helper allows callers to determine in advance whether subsequent __ptr_ring_produce() calls will succeed. This information can, for example, be used to temporarily stop producing until __ptr_ring_check_produce() indicates that space is available again. Co-developed-by: Tim Gebauer Signed-off-by: Tim Gebauer Acked-by: Michael S. Tsirkin Signed-off-by: Simon Schippers --- include/linux/ptr_ring.h | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h index d2c3629bbe45..c95e891903f0 100644 --- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h @@ -96,6 +96,20 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r) return ret; } +/* Note: callers invoking this in a loop must use a compiler barrier, + * for example cpu_relax(). Callers must hold producer_lock. + */ +static inline int __ptr_ring_check_produce(struct ptr_ring *r) +{ + if (unlikely(!r->size)) + return -EINVAL; + + if (data_race(r->queue[r->producer])) + return -ENOSPC; + + return 0; +} + /* Note: callers invoking this in a loop must use a compiler barrier, * for example cpu_relax(). Callers must hold producer_lock. * Callers are responsible for making sure pointer that is being queued @@ -103,8 +117,10 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r) */ static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr) { - if (unlikely(!r->size) || data_race(r->queue[r->producer])) - return -ENOSPC; + int p = __ptr_ring_check_produce(r); + + if (p) + return p; /* Make sure the pointer we are storing points to a valid data. */ /* Pairs with the dependency ordering in __ptr_ring_consume. */ -- 2.43.0