From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) (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 6F0B81A6838; Mon, 29 Jun 2026 10:46:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782730016; cv=none; b=jksthAn1qpu6K07BRd/NctWQ/T251I9USxq+yS08apxOr2r9RC0znPVl28AoTrPAfwYnU0AqRnYjUafSBnLNiTKCDTs80Efv7x0wlJSo3UFMEyRe/Phl2N5NFbyHi6yvxMPjBlLD6gKvJqivLKIz03DunYVuJyOL8MOzxXYYFdU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782730016; c=relaxed/simple; bh=/C0Q0DNvvO7li3qpeQ5jg51Bq60J4N/yY8q5r2HaP2s=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=rpMNSUo5bQe9GkTuZ4Jxst5GvmUTid9Sp7b9HZcNCrEP1XSwZuy8FOaWJFp8lGS9JwZtFKYlg/EDUhLqajuHhsFJyTix0NYsxxIqvrQ9dDY9oBkTqrtR8omPYRlUK9lN63qcxxHL0jY7xppypesiQvhulYk9DAwO9QWvAS6QdjU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf19.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 3C8B3C3217; Mon, 29 Jun 2026 10:46:47 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf19.hostedemail.com (Postfix) with ESMTPA id 7551E20028; Mon, 29 Jun 2026 10:46:45 +0000 (UTC) Date: Mon, 29 Jun 2026 06:47:21 -0400 From: Steven Rostedt To: Martin Weiss Cc: linux-kernel@vger.kernel.org, Martin Weiss , Masami Hiramatsu , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH] trace_branch: use per-cpu counters for correct/incorrect stats Message-ID: <20260629064721.1ffd75fb@gandalf.local.home> In-Reply-To: <20260629095838.601926-1-Martin.weiss2410@gmail.com> References: <20260629095838.601926-1-Martin.weiss2410@gmail.com> 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: wqsdokyfife11itnzjtgqonbz5e3m9ed X-Rspamd-Server: rspamout02 X-Rspamd-Queue-Id: 7551E20028 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+ZdPdIl2Oi15830NMDc9gVNDFIe3S3OQk= X-HE-Tag: 1782730005-880365 X-HE-Meta: U2FsdGVkX18i7nTH06hQ1lDgg3eDDBXMtir1jmPdtanWg0WK9dA9T5W6lZZs74YqMeioKKbQCDyUrfN7VI+aishisoGMdxFEU4fMBQuoTtqmRSMenoXok0B1DQuAVGsTThZPaomymVa32PHrNX4k0iGWkdsGsoKYSh/pM/AEb418V9BNBJzD/bQhw9Z/c8ay6d4oUz12JEreZdWI37hb9fMDpdQNUxjeH32fzC8Tvd7wHmB2H47k6TzzPU4qL0tbQAebDNlavnQAJX9CtKuxLbeTiPWWzUeQZlWpOj3eRaGzt0lgbr7c2ynwojreThTKctdZWy4z/TqoS+Nr8nxjGuCh8jZeldWA On Mon, 29 Jun 2026 16:58:38 +0700 Martin Weiss wrote: > Replace per-task counters with per-cpu increments to avoid race > conditions in the branch profiler fast path. > > Fixes FIXME about atomicity. > > Signed-off-by: Martin Weiss > --- > kernel/trace/trace_branch.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c > index d8e97ad798f0..960bcb3d7dbf 100644 > --- a/kernel/trace/trace_branch.c > +++ b/kernel/trace/trace_branch.c > @@ -213,11 +213,11 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, > */ > trace_likely_condition(f, val, expect); > > - /* FIXME: Make this atomic! */ > + /* use per-cpu counters to avoid contention */ > if (val == expect) > - f->data.correct++; > + this_cpu_inc(f->data.correct); > else > - f->data.incorrect++; > + this_cpu_inc(f->data.incorrect); I don't think this does what you think it does. Did you even test this? I'm guessing it would blow up in some fantastic ways. NAK. -- Steve > > user_access_restore(flags); > }