linux-kernel - Re: [PATCH] 2.6.18-rt7: fix more issues with 32-bit cycles_t in latency

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Date:	Mon, 04 Dec 2006 19:21:09 +0300
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	dwalker@...sta.com
Subject: Re: [PATCH] 2.6.18-rt7: fix more issues with 32-bit cycles_t in	latency_trace.c
 (take 3)

Hello.

Ingo Molnar wrote:

>>>i'd suggest to redo it - but please keep it simple and clean. Those 
>>>dozens of casts to u64 are quite ugly.

>>   Alas, there's *nothing* I can do about it with 32-bit cycles_t. 
>>[...]

> there's *always* a way to do such things more cleanly - such as the 
> patch below. Could you try to fix it up for 32-bit cycles_t platforms? I 
> bet the hackery will be limited to now() and maybe the conversion 
> routines, instead of spreading all around latency_trace.c.

    I'm not sure what you want me to do... You've switched to clocksource 
specific cycle_t (which is u64), do you want me to use the clocksource 
interface to get the cycles from now on?

> Index: linux/kernel/latency_trace.c
> ===================================================================
> --- linux.orig/kernel/latency_trace.c
> +++ linux/kernel/latency_trace.c
[...]
> @@ -1721,7 +1722,7 @@ check_critical_timing(int cpu, struct cp
>  	T2 = get_monotonic_cycles();
>  
>  	/* check for buggy clocks, handling wrap for 32-bit clocks */
> -	if (TYPE_EQUAL(cycles_t, unsigned long)) {
> +	if (TYPE_EQUAL(cycle_t, unsigned long)) {
>  		if (time_after((unsigned long)T1, (unsigned long)T2))
>  			printk("bug: %08lx < %08lx!\n",
>  				(unsigned long)T2, (unsigned long)T1);

    This earlier fix by Kevin woulnd't have sense anymore with cycle_t...

WBR, Sergei
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