From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4F8E42913; Tue, 21 Jan 2025 07:59:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737446346; cv=none; b=B8Td2WD4VnFZBKbnSmHdiRaudzFM00FLGk8i+0hVSSaQ0+S0dzbvQV14BSm/9dff6McwPNajhRTHcMpRNjCKLPTKquFLuRxDq3QeQEeBVJSWedANLONNi5vpIMxg3WiWq5I8Hpg8gXfwL+ReIqgK7raVociS8yrlzLG5c0TjtuI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737446346; c=relaxed/simple; bh=E2/bZ7VMntQ1oiUyzFadEi4P3H3GGSHYXxeM+aYMSFk=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=s0VWZg+vrNyevRZ5f2Y/lzIBCW8qjWPribUof0JCHED7N2myjkI630gK+nJObsCi9vK9jUnhGQvtrqG6yYC5kinjSkJQVV9cPiC3LXtzRJFrj8VStcVDxq692tj4i3JCbztbre+h/PkXkjV6kz8h524KK1z93G38PmAJ46D5VIY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=s8M4HOfo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="s8M4HOfo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E529AC4CEDF; Tue, 21 Jan 2025 07:59:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737446345; bh=E2/bZ7VMntQ1oiUyzFadEi4P3H3GGSHYXxeM+aYMSFk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=s8M4HOfoa4j8aMOLgzQmVTHOFTHq8xFzpirSabMz+eflWcysGeZ0kdAinATR+Z0Nc S0VnjKISaqNZIJH5A42LPyAG1ZV0WdV7QYN3Rz0+rE2vrbh49WGYe1rgmuzwcrNWw9 C1/pTDz/Q798nkWzEvbn6mh6oCDwu9Utx2laLnYpDpCnLD77fIn+xfWe0HKXw1aS7Z 0CYHsWeEupFF9i9QoOBuXTRJlYBeKfAM9qZRbLe0Qif6JWYy2tB38Z9NB8KIoSYRyh st20hSgZ2HlPEEScVtHOQr6SF6U8FLSLttbkGKEIWPowts3JCYf3wqr115oVziArsf TRv0QGYbfwcOQ== Date: Tue, 21 Jan 2025 16:59:02 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Peter Zijlstra , Thomas Gleixner , Linus Torvalds , Ludwig Rydberg , Andreas Larsson , stable@vger.kernel.org Subject: Re: [PATCH 1/2] ring-buffer: Do not allow events in NMI with generic atomic64 cmpxchg() Message-Id: <20250121165902.c671d578a19c0980c826eabb@kernel.org> In-Reply-To: <20250120235721.407068250@goodmis.org> References: <20250120235655.144537620@goodmis.org> <20250120235721.407068250@goodmis.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-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 On Mon, 20 Jan 2025 18:56:56 -0500 Steven Rostedt wrote: > From: Steven Rostedt > > Some architectures can not safely do atomic64 operations in NMI context. > Since the ring buffer relies on atomic64 operations to do its time > keeping, if an event is requested in NMI context, reject it for these > architectures. > Looks good to me. Reviewed-by: Masami Hiramatsu (Google) > Cc: stable@vger.kernel.org > Fixes: c84897c0ff592 ("ring-buffer: Remove 32bit timestamp logic") > Closes: https://lore.kernel.org/all/86fb4f86-a0e4-45a2-a2df-3154acc4f086@gaisler.com/ > Reported-by: Ludwig Rydberg > Signed-off-by: Steven Rostedt (Google) > --- > kernel/trace/ring_buffer.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 6d61ff78926b..b8e0ae15ca5b 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -4398,8 +4398,13 @@ rb_reserve_next_event(struct trace_buffer *buffer, > int nr_loops = 0; > int add_ts_default; > > - /* ring buffer does cmpxchg, make sure it is safe in NMI context */ > - if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && > + /* > + * ring buffer does cmpxchg as well as atomic64 operations > + * (which some archs use locking for atomic64), make sure this > + * is safe in NMI context > + */ > + if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) || > + IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) && > (unlikely(in_nmi()))) { > return NULL; > } > -- > 2.45.2 > > -- Masami Hiramatsu (Google)