linux-kernel - Re: [PATCH v7 2/2] tracing: Add support for preempt and irq enable/disable events

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Message-ID: <CAJWu+oq5h6PTuiNDS8GTaCWErSQuipCVq5_Oy+Cc6xbzQO_f8w@mail.gmail.com>
Date:   Wed, 4 Oct 2017 09:31:47 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, kernel-team@...roid.com,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v7 2/2] tracing: Add support for preempt and irq
 enable/disable events

Hi Peter,

On Wed, Oct 4, 2017 at 9:04 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, Sep 29, 2017 at 02:22:45PM -0700, Joel Fernandes wrote:
>> +++ b/kernel/trace/trace_irqsoff.c
>
>>  EXPORT_SYMBOL(trace_hardirqs_on);
>>  EXPORT_SYMBOL(trace_hardirqs_off);
>>  EXPORT_SYMBOL(trace_hardirqs_on_caller);
>>  EXPORT_SYMBOL(trace_hardirqs_off_caller);
>
> Steve, how does this compiler with lockdep enabled? Because:
>
> kernel/locking/lockdep.c:EXPORT_SYMBOL(trace_hardirqs_on_caller);
> kernel/locking/lockdep.c:EXPORT_SYMBOL(trace_hardirqs_on);
> kernel/locking/lockdep.c:EXPORT_SYMBOL(trace_hardirqs_off_caller);
> kernel/locking/lockdep.c:EXPORT_SYMBOL(trace_hardirqs_off);
>

These functions are defined in lockdep.c only with
CONFIG_PROVE_LOCKING, and in trace_irqsoff.c only for
!CONFIG_PROVE_LOCKING:
http://elixir.free-electrons.com/linux/latest/source/kernel/trace/trace_irqsoff.c#L463

I have tested these combinations and it compiles fine.

thanks,

- Joel