From nobody Mon Feb 9 05:41:15 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 ARC-Seal: i=1; a=rsa-sha256; t=1583825387; cv=none; d=zohomail.com; s=zohoarc; b=ba+isJEzKwBA5wO2vrwaiGvRJpqqT12QnEAVn7g5YG/pHyRlMtaKrG3CgbfGcE+stqF+R2FjfPVrEIurexlJ2qrr9PKL0lO9z8fDr/RPcwE+b0uKcoUjW5XNwIJA42/1MPa5rUmI4wb5chxgZJIs9Ygf/zqQ+WQKItRG1bsrM+U= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1583825387; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=4DS8yrXys/xAp7SLDygfZd4N1osZZYbMIOPQcxTP5Fw=; b=cUlgp3662FsMTyqZ8MHn+mySlUnsBRAYzGD/65AVr3aPz9J02TqvxC2iJVNhGqIoFCVuixXdOGVty3PMkayqhyESeZifde6QrLkwYh+WPIpx3C/FP2yzz8RXCrLO3Rl1/9X5cwo9vNE0f4Wd/fnkl6D13IPCJNA38JYztkC/esQ= ARC-Authentication-Results: i=1; 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 1583825387834793.0596365860459; Tue, 10 Mar 2020 00:29:47 -0700 (PDT) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jBZKG-0001dl-Mk; Tue, 10 Mar 2020 07:29:16 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jBZKF-0001dA-Pp for xen-devel@lists.xenproject.org; Tue, 10 Mar 2020 07:29:15 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id cfbf8984-62a0-11ea-ad1e-12813bfff9fa; Tue, 10 Mar 2020 07:29:01 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 43CC0AE34; Tue, 10 Mar 2020 07:28:59 +0000 (UTC) X-Inumbo-ID: cfbf8984-62a0-11ea-ad1e-12813bfff9fa X-Virus-Scanned: by amavisd-new at test-mx.suse.de From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Tue, 10 Mar 2020 08:28:52 +0100 Message-Id: <20200310072853.27567-6-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200310072853.27567-1-jgross@suse.com> References: <20200310072853.27567-1-jgross@suse.com> MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v4 5/6] 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 , Andrew Cooper , Ian Jackson , George Dunlap , Jan Beulich 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. While at it switch the rcu_read_[un]lock() implementation to static inline functions instead of macros. Signed-off-by: Juergen Gross --- V3: - add barriers to rcu_[en|dis]able() (Roger Pau Monn=C3=A9) - add rcu_quiesce_allowed() to ASSERT_NOT_IN_ATOMIC (Roger Pau Monn=C3=A9) - convert macros to static inline functions - add sanity check in rcu_read_unlock() V4: - use barrier() in rcu_[en|dis]able() (Julien Grall) --- xen/common/multicall.c | 1 + xen/common/preempt.c | 5 ++++- xen/common/rcupdate.c | 4 ++++ xen/common/softirq.c | 2 ++ xen/common/wait.c | 1 + xen/include/xen/rcupdate.h | 45 +++++++++++++++++++++++++++++++++++++++++-= --- 6 files changed, 53 insertions(+), 5 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/preempt.c b/xen/common/preempt.c index 3b4178fd44..8a351e644b 100644 --- a/xen/common/preempt.c +++ b/xen/common/preempt.c @@ -21,13 +21,15 @@ =20 #include #include +#include #include =20 DEFINE_PER_CPU(unsigned int, __preempt_count); =20 bool_t in_atomic(void) { - return preempt_count() || in_irq() || !local_irq_is_enabled(); + return preempt_count() || in_irq() || !local_irq_is_enabled() || + !rcu_quiesce_allowed(); } =20 #ifndef NDEBUG @@ -36,5 +38,6 @@ void ASSERT_NOT_IN_ATOMIC(void) ASSERT(!preempt_count()); ASSERT(!in_irq()); ASSERT(local_irq_is_enabled()); + ASSERT(rcu_quiesce_allowed()); } #endif diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c index 27d597bbeb..d1cc2f0a98 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 30beb27ae9..fd90b8511d 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 31c8b86d13..0f32b3c7d8 100644 --- a/xen/include/xen/rcupdate.h +++ b/xen/include/xen/rcupdate.h @@ -32,12 +32,42 @@ #define __XEN_RCUPDATE_H =20 #include +#include #include #include -#include +#include =20 #define __rcu =20 +#ifndef NDEBUG +DECLARE_PER_CPU(unsigned int, rcu_lock_cnt); + +static inline void rcu_quiesce_disable(void) +{ + this_cpu(rcu_lock_cnt)++; + barrier(); +} + +static inline void rcu_quiesce_enable(void) +{ + barrier(); + this_cpu(rcu_lock_cnt)--; +} + +static inline bool rcu_quiesce_allowed(void) +{ + return !this_cpu(rcu_lock_cnt); +} + +#else +static inline void rcu_quiesce_disable(void) { } +static inline void rcu_quiesce_enable(void) { } +static inline bool rcu_quiesce_allowed(void) +{ + return true; +} +#endif + /** * struct rcu_head - callback structure for use with RCU * @next: next update requests in a list @@ -91,16 +121,23 @@ 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(); }) +static inline void rcu_read_lock(rcu_read_lock_t *lock) +{ + 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(); }) +static inline void rcu_read_unlock(rcu_read_lock_t *lock) +{ + ASSERT(!rcu_quiesce_allowed()); + 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