From patchwork Wed Mar 25 10:55:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?SsO8cmdlbiBHcm/Dnw==?= X-Patchwork-Id: 11457479 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DF00A1668 for ; Wed, 25 Mar 2020 10:56:20 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C6BDB20722 for ; Wed, 25 Mar 2020 10:56:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C6BDB20722 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jH3h2-0005TO-L7; Wed, 25 Mar 2020 10:55:28 +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 1jH3h1-0005SO-1W for xen-devel@lists.xenproject.org; Wed, 25 Mar 2020 10:55:27 +0000 X-Inumbo-ID: 1bca5da0-6e87-11ea-85cc-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 1bca5da0-6e87-11ea-85cc-12813bfff9fa; Wed, 25 Mar 2020 10:55:16 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 50252ACC2; Wed, 25 Mar 2020 10:55:15 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Wed, 25 Mar 2020 11:55:10 +0100 Message-Id: <20200325105511.20882-5-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200325105511.20882-1-jgross@suse.com> References: <20200325105511.20882-1-jgross@suse.com> MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v7 4/5] 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 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 additional to 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). While at it switch the rcu_read_[un]lock() implementation to static inline functions instead of macros. Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich --- V3: - add barriers to rcu_[en|dis]able() (Roger Pau Monné) - add rcu_quiesce_allowed() to ASSERT_NOT_IN_ATOMIC (Roger Pau Monné) - convert macros to static inline functions - add sanity check in rcu_read_unlock() V4: - use barrier() in rcu_[en|dis]able() (Julien Grall) V5: - use rcu counter even if not using a debug build V6: - keep preempt_[dis|en]able() calls --- xen/common/rcupdate.c | 2 ++ xen/common/softirq.c | 4 +++- xen/include/xen/rcupdate.h | 37 ++++++++++++++++++++++++++++++++++--- 3 files changed, 39 insertions(+), 4 deletions(-) diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c index 12b89565d0..01b21951e0 100644 --- a/xen/common/rcupdate.c +++ b/xen/common/rcupdate.c @@ -46,6 +46,8 @@ #include #include +DEFINE_PER_CPU(unsigned int, rcu_lock_cnt); + /* 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 00d676b62c..eba65c5fc0 100644 --- a/xen/common/softirq.c +++ b/xen/common/softirq.c @@ -31,6 +31,8 @@ static void __do_softirq(unsigned long ignore_mask) unsigned long pending; bool rcu_allowed = !(ignore_mask & (1ul << RCU_SOFTIRQ)); + ASSERT(!rcu_allowed || rcu_quiesce_allowed()); + for ( ; ; ) { /* @@ -58,7 +60,7 @@ void process_pending_softirqs(void) (1ul << SCHED_SLAVE_SOFTIRQ); /* Block RCU processing in case of rcu_read_lock() held. */ - if ( preempt_count() ) + if ( !rcu_quiesce_allowed() ) ignore_mask |= 1ul << RCU_SOFTIRQ; ASSERT(!in_irq() && local_irq_is_enabled()); diff --git a/xen/include/xen/rcupdate.h b/xen/include/xen/rcupdate.h index 31c8b86d13..6f2587058e 100644 --- a/xen/include/xen/rcupdate.h +++ b/xen/include/xen/rcupdate.h @@ -32,12 +32,35 @@ #define __XEN_RCUPDATE_H #include +#include #include #include +#include #include #define __rcu +DECLARE_PER_CPU(unsigned int, rcu_lock_cnt); + +static inline void rcu_quiesce_disable(void) +{ + preempt_disable(); + this_cpu(rcu_lock_cnt)++; + barrier(); +} + +static inline void rcu_quiesce_enable(void) +{ + barrier(); + this_cpu(rcu_lock_cnt)--; + preempt_enable(); +} + +static inline bool rcu_quiesce_allowed(void) +{ + return !this_cpu(rcu_lock_cnt); +} + /** * struct rcu_head - callback structure for use with RCU * @next: next update requests in a list @@ -91,16 +114,24 @@ 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 or block while in an RCU read-side + * critical section. */ -#define rcu_read_lock(x) ({ ((void)(x)); preempt_disable(); }) +static inline void rcu_read_lock(rcu_read_lock_t *lock) +{ + rcu_quiesce_disable(); +} /** * 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(); +} /* * So where is rcu_write_lock()? It does not exist, as there is no