From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C152390235 for ; Mon, 1 Jun 2026 15:39:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780328352; cv=none; b=kVZeiCKr9ryEolf51t01gb7EGl9m8LjNF9/YORPGnqLlP6Mv0u04tgu0QWj0VpWuDz34i0wc2pYb/hQ8x62KRpyPs4N2OKR/Df7l1Iiefv6fQe4PiqJVu4KUUSiY2THn8lcHZt/cqe57pdJ8IUdaaGRJAS8Pr1rtsytRJm6h3LI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780328352; c=relaxed/simple; bh=aMI6ETwxmmNMEq4Pf/ssYWo3dsOyX8bUrocvUz48vCM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=Fzk2Ut/MAStNJMZqUEKFDMfG+B1DzqB3KQeAtcHMqOLRi3B8vcVNl/3CxbiZYeTvh2q5abki06oxPKh7Amleakts5ZWBX3E+RfkbiGvSFBuiCAxP3KifOXEv9p9NtBCPxL4ga0UYvl9yhUdZT+b4mGIUXjCaUo3gU2FS5prcyJ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=TIOs3b/Y; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TIOs3b/Y" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1780328349; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3TbSgf7lkZ2g4yFD6sbp+32F0/NjiAQOgCDqaL4CgCU=; b=TIOs3b/YRVWBStaWJsFhDnM6YqprrX1boMNgQVqAdqnynCYuw8xhA28Aes7Abcm/ORVP8r kEJ/yPw5kZTzjn6LBOlUvyrt2u+ao2tli+fMG+HcnkOVTGarXlNKL8OzeDwsMYmRpfHvs7 hp4L++ZKUMCdQEWAQz3a2FrnMaGEEco= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-42-VwEkJ4wQMs-5OCySIk01Aw-1; Mon, 01 Jun 2026 11:39:06 -0400 X-MC-Unique: VwEkJ4wQMs-5OCySIk01Aw-1 X-Mimecast-MFC-AGG-ID: VwEkJ4wQMs-5OCySIk01Aw_1780328343 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B1AEF1955F22; Mon, 1 Jun 2026 15:39:03 +0000 (UTC) Received: from fedora-pc.redhat.corp (headnet01.pony-001.prod.iad2.dc.redhat.com [10.2.32.101]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0168D18004A3; Mon, 1 Jun 2026 15:39:01 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Steven Rostedt , Gabriele Monaco , linux-trace-kernel@vger.kernel.org Cc: Wen Yang , Nam Cao Subject: [PATCH v4 05/13] rv: Fix monitor start ordering and memory ordering for monitoring flag Date: Mon, 1 Jun 2026 17:38:32 +0200 Message-ID: <20260601153840.124372-6-gmonaco@redhat.com> In-Reply-To: <20260601153840.124372-1-gmonaco@redhat.com> References: <20260601153840.124372-1-gmonaco@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-MFC-PROC-ID: VIhmDEUh8oU6BEVwVormKaUEOIwPomWdqxuS4ir3S0I_1780328343 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true From: Wen Yang da_monitor_start() set monitoring=1 before calling da_monitor_init_hook(), may racing with the sched_switch handler: da_monitor_start() sched_switch handler ------------------------- --------------------------------- da_mon->monitoring = 1; if (da_monitoring(da_mon)) /* true */ ha_start_timer_ns(...); /* hrtimer->base == NULL, crash */ da_monitor_init_hook(da_mon); /* hrtimer_setup() sets base */ Fix the ordering and pair with release/acquire semantics: da_monitor_init_hook(da_mon); smp_store_release(&da_mon->monitoring, 1); /* da_monitor_start() */ return smp_load_acquire(&da_mon->monitoring); /* da_monitoring() */ On ARM64 a plain STR + LDR does not form a release-acquire pair, so the load can observe monitoring=1 while hrtimer->base is still NULL. The plain accesses are also data races under KCSAN. Use WRITE_ONCE for the monitoring=0 store in da_monitor_reset() to cover the reset path. Fixes: 792575348ff7 ("rv/include: Add deterministic automata monitor definition via C macros") Signed-off-by: Wen Yang Reviewed-by: Gabriele Monaco Reviewed-by: Nam Cao Signed-off-by: Gabriele Monaco --- include/rv/da_monitor.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/include/rv/da_monitor.h b/include/rv/da_monitor.h index a7e103654..60dc39f26 100644 --- a/include/rv/da_monitor.h +++ b/include/rv/da_monitor.h @@ -82,7 +82,7 @@ static void react(enum states curr_state, enum events event) static inline void da_monitor_reset(struct da_monitor *da_mon) { da_monitor_reset_hook(da_mon); - da_mon->monitoring = 0; + WRITE_ONCE(da_mon->monitoring, 0); da_mon->curr_state = model_get_initial_state(); } @@ -95,8 +95,9 @@ static inline void da_monitor_reset(struct da_monitor *da_mon) static inline void da_monitor_start(struct da_monitor *da_mon) { da_mon->curr_state = model_get_initial_state(); - da_mon->monitoring = 1; da_monitor_init_hook(da_mon); + /* Pairs with smp_load_acquire in da_monitoring(). */ + smp_store_release(&da_mon->monitoring, 1); } /* @@ -104,7 +105,8 @@ static inline void da_monitor_start(struct da_monitor *da_mon) */ static inline bool da_monitoring(struct da_monitor *da_mon) { - return da_mon->monitoring; + /* Pairs with smp_store_release in da_monitor_start(). */ + return smp_load_acquire(&da_mon->monitoring); } /* -- 2.54.0