linux-kernel - Re: linux-next: Tree for Feb 4

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Message-ID: <CA+icZUX0iVY-Ng0xk6+4Du=2g5D1CudT54Y_ynmJkFA7dhWLHQ@mail.gmail.com>
Date:	Thu, 5 Feb 2015 15:57:12 +0100
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Dave Hansen <dave@...1.net>
Cc:	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-next <linux-next@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Kristen Carlson Accardi <kristen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: linux-next: Tree for Feb 4

On Thu, Feb 5, 2015 at 8:14 AM, Dave Hansen <dave@...1.net> wrote:
> On 02/04/2015 05:53 PM, Sedat Dilek wrote:
>> The architecture-specific switch_mm() function can be called by offline
>> CPUs, but includes event tracing, which cannot be legally carried out
>> on offline CPUs.  This results in a lockdep-RCU splat.  This commit fixes
>> this splat by omitting the tracing when the CPU is offline.
> ...
>>>> >> >                 load_cr3(next->pgd);
>>>> >> > -               trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
>>>> >> > +               if (cpu_online(smp_processor_id()))
>>>> >> > +                       trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
>
> Is this, perhaps, something that we should be doing in the generic trace
> code so that all of the trace users don't have to worry about it?  Also,
> this patch will add overhead to the code when tracing is off.  It would
> be best if we could manage to make the cpu_online() check only in the
> cases where the tracepoint is on.

Hi Dave,

thanks for your feedback.

I have just seen that I again see the call-trace.

Maybe you can discuss with Paul and others or offer a proposal patch.

I should really do something for my recovery (influenza).
Instead of laying lazy in my bed I thought to update my Linux kernels
and graphics driver stack which made me happy.


Regards,
- Sedat -
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