From patchwork Wed Nov 17 02:59:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Davidlohr Bueso X-Patchwork-Id: 520101 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6ED9C433EF for ; Wed, 17 Nov 2021 03:00:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D014B61B48 for ; Wed, 17 Nov 2021 03:00:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232822AbhKQDDX (ORCPT ); Tue, 16 Nov 2021 22:03:23 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:41834 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232852AbhKQDDV (ORCPT ); Tue, 16 Nov 2021 22:03:21 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 334CD212C9; Wed, 17 Nov 2021 03:00:22 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6407813BBF; Wed, 17 Nov 2021 03:00:19 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id UNNcDENwlGFefgAAMHmgww (envelope-from ); Wed, 17 Nov 2021 03:00:19 +0000 From: Davidlohr Bueso To: martin.petersen@oracle.com, jejb@linux.ibm.com Cc: hare@suse.de, bigeasy@linutronix.de, tglx@linutronix.de, linux-scsi@vger.kernel.org, linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, dave@stgolabs.net, Davidlohr Bueso Subject: [PATCH 2/3] scsi/fcoe: Add a local_lock to fcoe_percpu Date: Tue, 16 Nov 2021 18:59:55 -0800 Message-Id: <20211117025956.79616-3-dave@stgolabs.net> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20211117025956.79616-1-dave@stgolabs.net> References: <20211117025956.79616-1-dave@stgolabs.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org fcoe_get_paged_crc_eof() relies on the caller having preemption disabled to ensure the per-CPU fcoe_percpu context remains valid throughout the call. This is done by either holding spinlocks (such as bnx2fc_global_lock or qedf_global_lock) or the get_cpu() from fcoe_alloc_paged_crc_eof(). This last one breaks PREEMPT_RT semantics as there can be memory allocation and end up sleeping in atomic contexts. Introduce a local_lock_t to struct fcoe_percpu that will keep the non-RT case the same, mapping to preempt_disable/enable, while RT will use a per-CPU spinlock allowing the region to be preemptible but still maintain CPU locality. The other users of fcoe_percpu are already safe in this regard and do not require local_lock()ing. Signed-off-by: Davidlohr Bueso --- drivers/scsi/fcoe/fcoe.c | 6 ++++-- include/scsi/libfcoe.h | 2 ++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c index 6415f88738ad..a0064a1b4a32 100644 --- a/drivers/scsi/fcoe/fcoe.c +++ b/drivers/scsi/fcoe/fcoe.c @@ -1452,9 +1452,10 @@ static int fcoe_alloc_paged_crc_eof(struct sk_buff *skb, int tlen) struct fcoe_percpu_s *fps; int rc; - fps = &get_cpu_var(fcoe_percpu); + local_lock(&fcoe_percpu.lock); + fps = this_cpu_ptr(&fcoe_percpu); rc = fcoe_get_paged_crc_eof(skb, tlen, fps); - put_cpu_var(fcoe_percpu); + local_unlock(&fcoe_percpu.lock); return rc; } @@ -2487,6 +2488,7 @@ static int __init fcoe_init(void) p = per_cpu_ptr(&fcoe_percpu, cpu); INIT_WORK(&p->work, fcoe_receive_work); skb_queue_head_init(&p->fcoe_rx_list); + local_lock_init(&p->lock); } /* Setup link change notification */ diff --git a/include/scsi/libfcoe.h b/include/scsi/libfcoe.h index fac8e89aed81..6e79fb87fea2 100644 --- a/include/scsi/libfcoe.h +++ b/include/scsi/libfcoe.h @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -326,6 +327,7 @@ struct fcoe_percpu_s { struct sk_buff_head fcoe_rx_list; struct page *crc_eof_page; int crc_eof_offset; + local_lock_t lock; }; /**