From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) (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 0CD592E6133; Thu, 26 Jun 2025 15:36:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750952207; cv=none; b=Lf5UPNDwpAq/+fiRhoO/QVbwRVYJam4WqtIxnUJQG6MLDXcSJ2RaUd8XHsf3QDx/9KSrF6qRBbwY07qFbD51e/LImqyswW2R2TB+EucUH4BZV4WdEqgFwHu0vRCDBWbF1CDiUoeTU2xTaLRu9geiGh7bA0j/KTPot2hW5Q48GAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750952207; c=relaxed/simple; bh=wDC8jYentfesMeMpkJeR4ttf+wzbV1AWv04wos7u40w=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=GSy6zaLBDkLOnbh8+Xbz1iuuxdk5/pbMfYRO/qx4uRH8I2dF5MC36o1L7zBxKlP74iCSZ2NbwE/D8uNHypOz0ZV5Z+I8mIRwK8syxUhSEqiVpKgcmg1JS4BX5D0lJn66UOcBBwVC80ZzbBv9icclQhHP0bc/wDSMlXhvU5CEhEs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 7794B1A0287; Thu, 26 Jun 2025 15:36:44 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf11.hostedemail.com (Postfix) with ESMTPA id 87A6B20031; Thu, 26 Jun 2025 15:36:42 +0000 (UTC) Date: Thu, 26 Jun 2025 11:37:08 -0400 From: Steven Rostedt To: Nam Cao Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Gabriele Monaco , john.ogness@linutronix.de Subject: Re: [PATCH] tracing: Remove pointless memory barriers Message-ID: <20250626113708.4a96e47c@gandalf.local.home> In-Reply-To: <20250626113520.315db641@gandalf.local.home> References: <20250626151940.1756398-1-namcao@linutronix.de> <20250626113520.315db641@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: gcmfd58bhmc61ncuppn85sp3qbi9kgu3 X-Rspamd-Server: rspamout08 X-Rspamd-Queue-Id: 87A6B20031 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19/ljJA5rKjppQWXrxvRGDaMwWf8qKESsA= X-HE-Tag: 1750952202-303129 X-HE-Meta: U2FsdGVkX18ri2QmmzMURErDwCcIowdWfmK4u2wgAKljm2diZWhYl2M3BnCb7JBV9Bd6e2zYfM3IBZbvDvPx5qU+nDgOXkhoDdlYmLOsgnOPrWZkDdx2M8Hekpxlkc6nNkRbM200aOLYm3qxm/onOILYC7Lj490HjkXHPVU5BMVHD+UtWAoznA9OZOjWhbJQIq6lFigFP7/T36FA0JodScbea+wa4gaEmbIGgCq3pD/Q9VNWFoE0QK3RxaBj+vljT2ctDQIdBFtFOT3PAaaVcOM92OySNxHSm46UGGCg8LYOO3DgvKANlXBsFG4P9SDECJ/cgQgTNCe/pm+9tzbb33EwEq+taonUTBAfegputBCQ+bmXoQkgDw7hO83lexFBpbNKMK5MqChNtL9PnUn5mg== On Thu, 26 Jun 2025 11:35:20 -0400 Steven Rostedt wrote: > > @@ -2710,8 +2705,6 @@ void trace_buffered_event_enable(void) > > > > static void enable_trace_buffered_event(void *data) > > { > > - /* Probably not needed, but do it anyway */ > > - smp_rmb(); > > As the comment says, this one actually isn't needed, and yes, it can be > removed. One reason this isn't needed is because it's called via on_each_cpu() which will trigger its own barriers. -- Steve