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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A0711E7315D for ; Mon, 2 Feb 2026 12:55:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uEc8TvjnHa5ctWLyR7nKKcSQVtFV4OpS/QLW1YcL9eM=; b=Sc0YBmj/hTMgIy8OJqo0ZpuJ/t r1u9krN8lSkAZZCU9CVJA8l5hgVJrRsFvlyBt2gFVx5HWdAbW7xYzLFK5BWCGmsD2kfeyBBBVmhip LVh3jxuJdW7Z31nYhreHCCHax82Q3zfB8uL3TjFfnqiXIlJbXwv2oqzUyM18V1cQWrIV9voVMKkJC OqBzthShKnCptqCPLtYCUZ9z9t3YfNRDe5minYvqAJ2rTkGX2SSWlRSWpljDz8bXm3puj6pip4dmg v50eavh4XNpxCtR2gCil62IDJh3kdYT/pAW56aoq2q08NJf0Xbfcs6fdzFaEOaUmvq0cSReadtXJg v7l5Xnyg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vmtSB-00000004yQF-1mNP; Mon, 02 Feb 2026 12:54:55 +0000 Received: from smtpout-02.galae.net ([185.246.84.56]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vmtS7-00000004yPY-2GkF for linux-arm-kernel@lists.infradead.org; Mon, 02 Feb 2026 12:54:53 +0000 Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id B82DE1A2B9D; Mon, 2 Feb 2026 12:54:40 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 887B360767; Mon, 2 Feb 2026 12:54:40 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 58917119A8891; Mon, 2 Feb 2026 13:54:35 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1770036879; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=uEc8TvjnHa5ctWLyR7nKKcSQVtFV4OpS/QLW1YcL9eM=; b=O0uWghrHWXwaACUvUJKHzbTu4QLw59L0R/2S+wlYL3pxoyfqk9f0c54BD6+7bowN2+12Ss awylkXRFZduyC7o/tZRzRy2Y+FvEl1fsjer/2iNtWqE/oeazmwF3OdJC12pTpFjuFmM6d+ SYqN8LApm6ddErnuQWEuzOo1BYdvSHbo1dsSl9jtjZA5xK06bTDVCqU3aFNMMOC5oduXzS MeezuuwwWFo2CucaaYP2gfY8ktltTJ2J4ubZEYqcAr2ahRPaIxtr9G64JSWFY/FtIQG18m sr5VJPZ5L4V3rQ7mAIYfmfJxvp4PfwYEagT1VRqllmmwKQRaI87K3GNxXGD59w== Message-ID: <825baaef-bd76-4e2c-94ef-3daddf55243b@bootlin.com> Date: Mon, 2 Feb 2026 13:54:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] soc: fsl: qbman: fix race condition in qman_destroy_fq To: Christophe Leroy , Marco Crivellari , Kees Cook , Roy Pledge , Claudiu Manoil , Scott Wood Cc: Thomas Petazzoni , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, CHAMPSEIX Thomas References: <20251223072549.397625-1-richard.genoud@bootlin.com> From: Richard GENOUD Content-Language: en-US, fr Organization: Bootlin In-Reply-To: <20251223072549.397625-1-richard.genoud@bootlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260202_045451_719555_9D0434D0 X-CRM114-Status: GOOD ( 26.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Le 23/12/2025 à 08:25, Richard Genoud a écrit : > When QMAN_FQ_FLAG_DYNAMIC_FQID is set, there's a race condition between > fq_table[fq->idx] state and freeing/allocating from the pool and > WARN_ON(fq_table[fq->idx]) in qman_create_fq() gets triggered. > > Indeed, we can have: > Thread A Thread B > qman_destroy_fq() qman_create_fq() > qman_release_fqid() > qman_shutdown_fq() > gen_pool_free() > -- At this point, the fqid is available again -- > qman_alloc_fqid() > -- so, we can get the just-freed fqid in thread B -- > fq->fqid = fqid; > fq->idx = fqid * 2; > WARN_ON(fq_table[fq->idx]); > fq_table[fq->idx] = fq; > fq_table[fq->idx] = NULL; > > And adding some logs between qman_release_fqid() and > fq_table[fq->idx] = NULL makes the WARN_ON() trigger a lot more. > > To prevent that, ensure that fq_table[fq->idx] is set to NULL before > gen_pool_free() is called by using smp_wmb(). > Tested on a LS1046A based board. With this patch, the warning is not triggered anymore. Tested-by: CHAMPSEIX Thomas > Fixes: c535e923bb97 ("soc/fsl: Introduce DPAA 1.x QMan device driver") > Signed-off-by: Richard Genoud > --- > drivers/soc/fsl/qbman/qman.c | 24 ++++++++++++++++++++++-- > 1 file changed, 22 insertions(+), 2 deletions(-) > > NB: I'm not 100% sure of the need of a barrier here, since even without > it, the WARN_ON() wasn't triggered any more. > > diff --git a/drivers/soc/fsl/qbman/qman.c b/drivers/soc/fsl/qbman/qman.c > index 6b392b3ad4b1..39a3e7aab6ff 100644 > --- a/drivers/soc/fsl/qbman/qman.c > +++ b/drivers/soc/fsl/qbman/qman.c > @@ -1827,6 +1827,8 @@ EXPORT_SYMBOL(qman_create_fq); > > void qman_destroy_fq(struct qman_fq *fq) > { > + int leaked; > + > /* > * We don't need to lock the FQ as it is a pre-condition that the FQ be > * quiesced. Instead, run some checks. > @@ -1834,11 +1836,29 @@ void qman_destroy_fq(struct qman_fq *fq) > switch (fq->state) { > case qman_fq_state_parked: > case qman_fq_state_oos: > - if (fq_isset(fq, QMAN_FQ_FLAG_DYNAMIC_FQID)) > - qman_release_fqid(fq->fqid); > + /* > + * There's a race condition here on releasing the fqid, > + * setting the fq_table to NULL, and freeing the fqid. > + * To prevent it, this order should be respected: > + */ > + if (fq_isset(fq, QMAN_FQ_FLAG_DYNAMIC_FQID)) { > + leaked = qman_shutdown_fq(fq->fqid); > + if (leaked) > + pr_debug("FQID %d leaked\n", fq->fqid); > + } > > DPAA_ASSERT(fq_table[fq->idx]); > fq_table[fq->idx] = NULL; > + > + if (fq_isset(fq, QMAN_FQ_FLAG_DYNAMIC_FQID) && !leaked) { > + /* > + * fq_table[fq->idx] should be set to null before > + * freeing fq->fqid otherwise it could by allocated by > + * qman_alloc_fqid() while still being !NULL > + */ > + smp_wmb(); > + gen_pool_free(qm_fqalloc, fq->fqid | DPAA_GENALLOC_OFF, 1); > + } > return; > default: > break; > > base-commit: 9448598b22c50c8a5bb77a9103e2d49f134c9578 -- Richard Genoud, Bootlin Embedded Linux and Kernel engineering https://bootlin.com