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Date:   Tue, 12 Dec 2023 09:16:54 +0000
From:   Will Deacon <will@kernel.org>
To:     Robin Murphy <robin.murphy@arm.com>, catalin.marinas@arm.com
Cc:     mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, jeremy.linton@arm.com,
        ilkka@os.amperecomputing.com, renyu.zj@linux.alibaba.com
Subject: Re: [PATCH] perf/arm-cmn: Fail DTC counter allocation correctly
Message-ID: <20231212091654.GA28174@willie-the-truck>
References: <ed589c0d8e4130dc68b8ad1625226d28bdc185d4.1702322847.git.robin.murphy@arm.com>
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On Mon, Dec 11, 2023 at 07:27:28PM +0000, Robin Murphy wrote:
> Calling arm_cmn_event_clear() before all DTC indices are allocated is
> wrong, and can lead to arm_cmn_event_add() erroneously clearing live
> counters from full DTCs where allocation fails. Since the DTC counters
> are only updated by arm_cmn_init_counter() after all DTC and DTM
> allocations succeed, nothing actually needs cleaning up in this case
> anyway, and it should just return directly as it did before.
> 
> Fixes: 7633ec2c262f ("perf/arm-cmn: Rework DTC counters (again)")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/perf/arm-cmn.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
> index 86d970e74129..c584165b13ba 100644
> --- a/drivers/perf/arm-cmn.c
> +++ b/drivers/perf/arm-cmn.c
> @@ -1816,7 +1816,7 @@ static int arm_cmn_event_add(struct perf_event *event, int flags)
>  			idx = 0;
>  			while (cmn->dtc[j].counters[idx])
>  				if (++idx == CMN_DT_NUM_COUNTERS)
> -					goto free_dtms;
> +					return -ENOSPC;
>  		}
>  		hw->dtc_idx[j] = idx;
>  	}
> -- 
> 2.39.2.101.g768bb238c484.dirty

Acked-by: Will Deacon <will@kernel.org>

Catalin -- please can you take this one as a fix?

Cheers,

Will