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To:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Kan Liang <kan.liang@linux.intel.com>,
        Jin Yao <yao.jin@linux.intel.com>
From:   John Garry <john.garry@huawei.com>
Subject: [bug report] Patch "perf tools: Fix pattern matching for same
 substring in different pmu type" broken
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-perf-users@vger.kernel.org" <linux-perf-users@vger.kernel.org>,
        Zhangshaokun <zhangshaokun@hisilicon.com>,
        "liuqi (BA)" <liuqi115@huawei.com>
Message-ID: <44e25825-5f23-c641-9f1c-72268d895f75@huawei.com>
Date:   Mon, 19 Jul 2021 15:13:06 +0100
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Hi guys,

The named patch has broken PMU alias matching on my arm64 system.

Specifically it is broken for when multiple tokens are used in the 
alias. For example, alias "hisi_sccl,l3c" would previously match for PMU 
"hisi_sccl3_l3c7", but that no longer works.

In my example, in looking at the code, the callchain 
pmu_uncore_alias_match("hisi_sccl,l3c", "hisi_sccl3_l3c7") -> 
per_pmu__valid_suffix("hisi_sccl3_l3c7", "hisi_sccl") fails in the 
following check:

static bool perf_pmu__valid_suffix(char *pmu_name, char *tok)
{
	char *p;
	...
	p = pmu_name + strlen(tok);
	...
	if (*p != '_') //here
		return false;
}

This check assumes the first token must be followed by a '_', but it is 
possibly a numeric.

Please let me know how this should work. Previously it would match on 
the tokens, ignoring numerics and '_'.

As an aside, I'll look at why our testcases don't cover this scenario 
and look to add a test if necessary.

Thanks,
john

Ps, please cc linux-perf-users@vger.kernel.org as in the MAINTAINERS 
file in future, as not all subscribe to the open kernel list (and so 
cannot easily reply directly).