From nobody Mon Feb 9 07:23:06 2026 Delivered-To: importer@patchew.org Received-SPF: none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1582028524949342.1652007758996; Tue, 18 Feb 2020 04:22:04 -0800 (PST) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1j41sY-0006fk-O9; Tue, 18 Feb 2020 12:21:30 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1j41sX-0006fK-Pl for xen-devel@lists.xenproject.org; Tue, 18 Feb 2020 12:21:29 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 2a3f902e-5249-11ea-bc8e-bc764e2007e4; Tue, 18 Feb 2020 12:21:18 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 0D51EB369; Tue, 18 Feb 2020 12:21:18 +0000 (UTC) X-Inumbo-ID: 2a3f902e-5249-11ea-bc8e-bc764e2007e4 X-Virus-Scanned: by amavisd-new at test-mx.suse.de From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Tue, 18 Feb 2020 13:21:14 +0100 Message-Id: <20200218122114.17596-5-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200218122114.17596-1-jgross@suse.com> References: <20200218122114.17596-1-jgross@suse.com> Subject: [Xen-devel] [PATCH v2 4/4] xen/rcu: add assertions to debug build X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Stefano Stabellini , Julien Grall , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ian Jackson , Jan Beulich MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Xen's RCU implementation relies on no softirq handling taking place while being in a RCU critical section. Add ASSERT()s in debug builds in order to catch any violations. For that purpose modify rcu_read_[un]lock() to use a dedicated percpu counter instead of preempt_[en|dis]able() as this enables to test that condition in __do_softirq() (ASSERT_NOT_IN_ATOMIC() is not usable there due to __cpu_up() calling process_pending_softirqs() while holding the cpu hotplug lock). Dropping the now no longer needed #include of preempt.h in rcupdate.h requires adding it in some sources. Signed-off-by: Juergen Gross --- xen/common/multicall.c | 1 + xen/common/rcupdate.c | 4 ++++ xen/common/softirq.c | 2 ++ xen/common/wait.c | 1 + xen/include/xen/rcupdate.h | 21 +++++++++++++++++---- 5 files changed, 25 insertions(+), 4 deletions(-) diff --git a/xen/common/multicall.c b/xen/common/multicall.c index 5a199ebf8f..67f1a23485 100644 --- a/xen/common/multicall.c +++ b/xen/common/multicall.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c index e6add0b120..b03f4b44d9 100644 --- a/xen/common/rcupdate.c +++ b/xen/common/rcupdate.c @@ -46,6 +46,10 @@ #include #include =20 +#ifndef NDEBUG +DEFINE_PER_CPU(unsigned int, rcu_lock_cnt); +#endif + /* Global control variables for rcupdate callback mechanism. */ static struct rcu_ctrlblk { long cur; /* Current batch number. */ diff --git a/xen/common/softirq.c b/xen/common/softirq.c index 3fe75ca3e8..18be8db0c6 100644 --- a/xen/common/softirq.c +++ b/xen/common/softirq.c @@ -30,6 +30,8 @@ static void __do_softirq(unsigned long ignore_mask, bool = rcu_allowed) unsigned int i, cpu; unsigned long pending; =20 + ASSERT(!rcu_allowed || rcu_quiesce_allowed()); + for ( ; ; ) { /* diff --git a/xen/common/wait.c b/xen/common/wait.c index 24716e7676..9cdb174036 100644 --- a/xen/common/wait.c +++ b/xen/common/wait.c @@ -19,6 +19,7 @@ * along with this program; If not, see . */ =20 +#include #include #include #include diff --git a/xen/include/xen/rcupdate.h b/xen/include/xen/rcupdate.h index 87f35b7704..a5ee7fec2b 100644 --- a/xen/include/xen/rcupdate.h +++ b/xen/include/xen/rcupdate.h @@ -34,10 +34,23 @@ #include #include #include -#include +#include =20 #define __rcu =20 +#ifndef NDEBUG +DECLARE_PER_CPU(unsigned int, rcu_lock_cnt); + +#define rcu_quiesce_disable() (this_cpu(rcu_lock_cnt))++ +#define rcu_quiesce_enable() (this_cpu(rcu_lock_cnt))-- +#define rcu_quiesce_allowed() (!this_cpu(rcu_lock_cnt)) + +#else +#define rcu_quiesce_disable() ((void)0) +#define rcu_quiesce_enable() ((void)0) +#define rcu_quiesce_allowed() true +#endif + /** * struct rcu_head - callback structure for use with RCU * @next: next update requests in a list @@ -90,16 +103,16 @@ typedef struct _rcu_read_lock rcu_read_lock_t; * will be deferred until the outermost RCU read-side critical section * completes. * - * It is illegal to block while in an RCU read-side critical section. + * It is illegal to process softirqs while in an RCU read-side critical se= ction. */ -#define rcu_read_lock(x) ({ ((void)(x)); preempt_disable(); }) +#define rcu_read_lock(x) ({ ((void)(x)); rcu_quiesce_disable(); }) =20 /** * rcu_read_unlock - marks the end of an RCU read-side critical section. * * See rcu_read_lock() for more information. */ -#define rcu_read_unlock(x) ({ ((void)(x)); preempt_enable(); }) +#define rcu_read_unlock(x) ({ ((void)(x)); rcu_quiesce_enable(); }) =20 /* * So where is rcu_write_lock()? It does not exist, as there is no --=20 2.16.4 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel