linux-kernel - Re: [PATCH] MIPS: perf: fix deadlock

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Message-ID: <20170406091604.37poma56ptmcn7de@hirez.programming.kicks-ass.net>
Date:   Thu, 6 Apr 2017 11:16:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Rabin Vincent <rabin.vincent@...s.com>
Cc:     ralf@...ux-mips.org, linux-mips@...ux-mips.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, Rabin Vincent <rabinv@...s.com>
Subject: Re: [PATCH] MIPS: perf: fix deadlock

On Wed, Apr 05, 2017 at 03:14:08PM +0200, Rabin Vincent wrote:

That lock is disgusting... but yes patch looks about right.

I'll leave it to the MIPS people though.

> ---
>  arch/mips/kernel/perf_event_mipsxx.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/mips/kernel/perf_event_mipsxx.c b/arch/mips/kernel/perf_event_mipsxx.c
> index 8c35b31..9452b02 100644
> --- a/arch/mips/kernel/perf_event_mipsxx.c
> +++ b/arch/mips/kernel/perf_event_mipsxx.c
> @@ -1446,6 +1446,11 @@ static int mipsxx_pmu_handle_shared_irq(void)
>  	HANDLE_COUNTER(0)
>  	}
>  
> +#ifdef CONFIG_MIPS_PERF_SHARED_TC_COUNTERS
> +	read_unlock(&pmuint_rwlock);
> +#endif
> +	resume_local_counters();
> +
>  	/*
>  	 * Do all the work for the pending perf events. We can do this
>  	 * in here because the performance counter interrupt is a regular
> @@ -1454,10 +1459,6 @@ static int mipsxx_pmu_handle_shared_irq(void)
>  	if (handled == IRQ_HANDLED)
>  		irq_work_run();
>  
> -#ifdef CONFIG_MIPS_PERF_SHARED_TC_COUNTERS
> -	read_unlock(&pmuint_rwlock);
> -#endif
> -	resume_local_counters();
>  	return handled;
>  }
>  
> -- 
> 2.7.0
>