From: Daniel Bristot de Oliveira <bristot@redhat.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
"H. Peter Anvin" <hpa@zytor.com>, Jiri Olsa <jolsa@redhat.com>,
Namhyung Kim <namhyung@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>,
Romulo Silva de Oliveira <romulo.deoliveira@ufsc.br>,
paulmck@linux.vnet.ibm.com, Clark Williams <williams@redhat.com>,
x86@kernel.org
Subject: Re: [RFC PATCH 0/7] Early task context tracking
Date: Mon, 8 Apr 2019 14:54:54 +0200 [thread overview]
Message-ID: <09416831-0c99-16ea-9ff0-128dd75f1b1f@redhat.com> (raw)
In-Reply-To: <20190404174037.GA183378@google.com>
On 4/4/19 7:40 PM, Joel Fernandes wrote:
>> Currently, recursion control uses the preempt_counter to
>> identify the current context. The NMI/HARD/SOFT IRQ counters
>> are set in the preempt_counter in the irq_enter/exit functions.
> Just started looking.
>
> Thinking out loud... can we not just update the preempt_count as early on
> entry and as late on exit, as possible, and fix it that way? (Haven't fully
> yet looked into what could break if we did that.)
>
> I also feel the context tracking should be unified, right now we already have
> two methods AFAIK - preempt_count and lockdep. Now this is yet another third.
> Granted lockdep cannot be enabled in production, but still. It will be nice
> to unify these tracking methods and if there is a single point of all such
> context tracking that works well, and even better if we can just fix
> preempt_count and use that for non-debugging usecases.
>
> Also I feel in_interrupt() etc should be updated to rely on such tracking
> methods if something other than preempt_count is used..
Hi Joel,
I agree with you that it is important to have a single method to identify the
context.
I did the RFC using a specific percpu variable to make things simpler. Also
because I tried to move set/unset of the preempt_counter and my dev VM stopped
booting. So it looked, somehow, risky to move the preempt_counter.
Still, if people believe it is better to use the preempt_counter... I am not
against...
-- Daniel
> thanks,
>
> - Joel
>
>
prev parent reply other threads:[~2019-04-08 12:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 20:03 [RFC PATCH 0/7] Early task context tracking Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 1/7] x86/entry: Add support for early " Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 2/7] trace: Move the trace recursion context enum to trace.h and reuse it Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 3/7] trace: Optimize trace_get_context_bit() Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 4/7] trace/ring_buffer: Use trace_get_context_bit() Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 5/7] trace: Use early task context tracking if available Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 6/7] events: Create an trace_get_context_bit() Daniel Bristot de Oliveira
2019-04-02 20:03 ` [RFC PATCH 7/7] events: Use early task context tracking if available Daniel Bristot de Oliveira
2019-04-04 0:01 ` [RFC PATCH 0/7] Early task context tracking Andy Lutomirski
2019-04-04 9:42 ` Peter Zijlstra
2019-04-08 12:47 ` Daniel Bristot de Oliveira
2019-04-08 16:08 ` Andy Lutomirski
2019-04-04 17:40 ` Joel Fernandes
2019-04-08 12:54 ` Daniel Bristot de Oliveira [this message]
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