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 857F028FA80; Tue, 13 May 2025 17:56:28 +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=1747158988; cv=none; b=hvaEL+G14YVaPX/IOhF4/bGttrLE5WITScGoFyHL/2cjoQbccGZ2TtfJmzBUtOCS1S+9008NBTSVS0upQrnpO1ap4wf8bZw1QY8wFtYvq0ZKGZ13KgNmhKq8cDnisjQg+9hrc3mawnK9Z1C8+Aj2A2YvguLjmHetYawORaUHVnM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747158988; c=relaxed/simple; bh=bFeWglMtZyemmFzY0JIixKNIr3nFEUUNL00dLPgu/J8=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Xbxgf1XEWxksMY9fDn1bVmWamHPztyPpexS27O1tCc19/VMtVPdpuy1RCiDNUsEON+1N5eqOTj6wifkV7ZnmjJa6rxd86ICwNC0PMoAp41jjK/AgtSiNv6yO+W5QxVg6bqdzvizJqzlO87nhoevEoedwL+5nma6ed7GB9zu9aIg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DC89C4CEEB; Tue, 13 May 2025 17:56:27 +0000 (UTC) Date: Tue, 13 May 2025 13:56:51 -0400 From: Steven Rostedt To: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3] tracing: Record trace_clock and recover when reboot Message-ID: <20250513135652.7cb970cf@gandalf.local.home> In-Reply-To: <174709628747.1945884.11884057542151507891.stgit@mhiramat.tok.corp.google.com> References: <174709628747.1945884.11884057542151507891.stgit@mhiramat.tok.corp.google.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 On Tue, 13 May 2025 09:31:27 +0900 "Masami Hiramatsu (Google)" wrote: > From: Masami Hiramatsu (Google) > > Record trace_clock information in the trace_scratch area and recover > the trace_clock when boot, so that reader can docode the timestamp > correctly. > Note that since most trace_clocks records the timestamp in nano- > seconds, this is not a bug. But some trace_clock, like counter and > tsc will record the counter value. Only for those trace_clock user > needs this information. > > Signed-off-by: Masami Hiramatsu (Google) > --- > Changes in v3: > - Save clock_id instead of its name. > Changes in v2: > - instead of exposing it via last_boot_info, set the current > trace_clock as the same clock we used in the last boot. > --- > kernel/trace/trace.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index cf51c30b137f..2a060c62d686 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -6066,6 +6066,7 @@ struct trace_mod_entry { > }; > > struct trace_scratch { > + int clock_id; Should be "unsigned int" > unsigned long text_addr; > unsigned long nr_entries; > struct trace_mod_entry entries[]; > @@ -6181,6 +6182,7 @@ static void update_last_data(struct trace_array *tr) > if (tr->scratch) { > struct trace_scratch *tscratch = tr->scratch; > > + tscratch->clock_id = tr->clock_id; > memset(tscratch->entries, 0, > flex_array_size(tscratch, entries, tscratch->nr_entries)); > tscratch->nr_entries = 0; > @@ -7403,6 +7405,12 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr) > tracing_reset_online_cpus(&tr->max_buffer); > #endif > > + if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) { > + struct trace_scratch *tscratch = tr->scratch; > + > + tscratch->clock_id = i; > + } > + > mutex_unlock(&trace_types_lock); > > return 0; > @@ -9628,6 +9636,14 @@ static void setup_trace_scratch(struct trace_array *tr, > > /* Scan modules to make text delta for modules. */ > module_for_each_mod(make_mod_delta, tr); > + > + /* Set trace_clock as the same of the previous boot. */ > + if (tscratch->clock_id != tr->clock_id) { > + if (tracing_set_clock(tr, trace_clocks[tscratch->clock_id].name) < 0) { In case the tscratch->clock_id gets corrupted, we better make sure it doesn't overflow: if (tscratch->clock_id >= ARRAY_SIZE(trace_clocks) || tracing_set_clock(tr, trace_clocks[tscratch->clock_id].name) < 0) { -- Steve > + pr_info("the previous trace_clock info is not valid."); > + goto reset; > + } > + } > return; > reset: > /* Invalid trace modules */