linux-kernel - Re: Performance Events hangs with Intel P4 system

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Message-ID: <20100514115655.GA18069@elte.hu>
Date:	Fri, 14 May 2010 13:56:55 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Jaswinder Singh Rajput <jaswinderlinux@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: Performance Events hangs with Intel P4 system


* Lin Ming <ming.m.lin@...el.com> wrote:

> p4_event_bind::cntr is "unsigned char".
> But p4_next_cntr has return type of "int".
> So the explicit conversion is needed to get the correct result. 

> @@ -780,7 +780,7 @@ static int p4_pmu_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign
>  		if (unlikely(escr_idx == -1))
>  			goto done;
>  
> -		if (hwc->idx != -1 && !p4_should_swap_ts(hwc->config, cpu)) {
> +		if (hwc->idx != (unsigned char)-1 && !p4_should_swap_ts(hwc->config, cpu)) {

That cast is _extremely_ ugly. Please fix the signedness of the types instead.

	Ingo
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