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 X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B775C433DF for ; Wed, 27 May 2020 20:11:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 53CB22073B for ; Wed, 27 May 2020 20:11:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728650AbgE0ULi (ORCPT ); Wed, 27 May 2020 16:11:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728587AbgE0ULa (ORCPT ); Wed, 27 May 2020 16:11:30 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02F40C03E96E for ; Wed, 27 May 2020 13:11:29 -0700 (PDT) Received: from localhost ([127.0.0.1] helo=flow.W.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1je2Od-0005ku-Du; Wed, 27 May 2020 22:11:27 +0200 From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Steven Rostedt , Will Deacon , Thomas Gleixner , "Paul E . McKenney" , Linus Torvalds , Matthew Wilcox , Mike Galbraith , Minchan Kim , Nitin Gupta , Sergey Senozhatsky , Sebastian Andrzej Siewior Subject: [PATCH v3 7/7] zram: Use local lock to protect per-CPU data Date: Wed, 27 May 2020 22:11:19 +0200 Message-Id: <20200527201119.1692513-8-bigeasy@linutronix.de> X-Mailer: git-send-email 2.27.0.rc0 In-Reply-To: <20200527201119.1692513-1-bigeasy@linutronix.de> References: <20200527201119.1692513-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mike Galbraith The zcomp driver uses per-CPU compression. The per-CPU data pointer is acquired with get_cpu_ptr() which implicitly disables preemption. It allocates memory inside the preempt disabled region which conflicts with the PREEMPT_RT semantics. Replace the implicit preemption control with an explicit local lock. This allows RT kernels to substitute it with a real per CPU lock, which serializes the access but keeps the code section preemptible. On non RT kernels this maps to preempt_disable() as before, i.e. no functional change. [bigeasy: Use local_lock(), description, drop reordering] Cc: Minchan Kim Cc: Nitin Gupta Cc: Sergey Senozhatsky Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- drivers/block/zram/zcomp.c | 7 +++++-- drivers/block/zram/zcomp.h | 3 +++ 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index 912e3e63d8a09..5ee8e3fae5516 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -110,12 +110,13 @@ ssize_t zcomp_available_show(const char *comp, char *= buf) =20 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp) { - return get_cpu_ptr(comp->stream); + local_lock(&comp->stream->lock); + return this_cpu_ptr(comp->stream); } =20 void zcomp_stream_put(struct zcomp *comp) { - put_cpu_ptr(comp->stream); + local_unlock(&comp->stream->lock); } =20 int zcomp_compress(struct zcomp_strm *zstrm, @@ -159,6 +160,8 @@ int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist= _node *node) int ret; =20 zstrm =3D per_cpu_ptr(comp->stream, cpu); + local_lock_init(&zstrm->lock); + ret =3D zcomp_strm_init(zstrm, comp); if (ret) pr_err("Can't allocate a compression stream\n"); diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h index 72c2ee4d843ed..40f6420f4b2e9 100644 --- a/drivers/block/zram/zcomp.h +++ b/drivers/block/zram/zcomp.h @@ -5,8 +5,11 @@ =20 #ifndef _ZCOMP_H_ #define _ZCOMP_H_ +#include =20 struct zcomp_strm { + /* The members ->buffer and ->tfm are protected by ->lock. */ + local_lock_t lock; /* compression/decompression buffer */ void *buffer; struct crypto_comp *tfm; --=20 2.27.0.rc0