linux-kernel - Re: [PATCH v4 net-next] net: poll/select low latency socket support

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Date:	Thu, 27 Jun 2013 17:29:58 -0700
From:	Cody P Schafer <devel-lists@...yps.com>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
CC:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	e1000-devel@...ts.sourceforge.net,
	Willem de Bruijn <willemb@...gle.com>,
	Eric Dumazet <erdnetdev@...il.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Amir Vadai <amirv@...lanox.com>,
	Alex Rosenbaum <alexr@...lanox.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v4 net-next] net: poll/select low latency socket support

On 06/27/2013 05:25 PM, Cody P Schafer wrote:
> On 06/24/2013 12:28 AM, Eliezer Tamir wrote:
>> select/poll busy-poll support.
>> ...
>
> I'm seeing warnings about using smp_processor_id() while preemptable
> (log included below) due to this patch. I expect the use of
> ll_end_time() -> sched_clock() here is triggering this.
>
> Apologies if this has already been noted.

To be clear, given how sched_time() is used here the BUG appears 
invalid, but we need a way to mark this as OK for the smp_processor_id() 
checks so we don't get BUG spam.

> --
>
> # [    3.114452] BUG: using smp_processor_id() in preemptible [00000000]
> code: sh/62
...
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