linux-kernel - [PATCH] perf tools: Refactor precise

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Message-ID: <20251022220802.1335131-1-zide.chen@intel.com>
Date: Wed, 22 Oct 2025 15:08:02 -0700
From: Zide Chen <zide.chen@...el.com>
To: linux-kernel@...r.kernel.org
Cc: linux-perf-users@...r.kernel.org,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	thomas.falcon@...el.com,
	dapeng1.mi@...ux.intel.com,
	xudong.hao@...el.com,
	Zide Chen <zide.chen@...el.com>
Subject: [PATCH] perf tools: Refactor precise_ip fallback logic

Commit c33aea446bf555ab ("perf tools: Fix precise_ip fallback logic")
unconditionally called the precise_ip fallback and moved it after the
missing-feature checks so that it could handle EINVAL as well.

However, this introduced an issue: after disabling missing features,
the event could fail to open, which makes the subsequent precise_ip
fallback useless since it will always fail.

For example, run the following command on Intel SPR:

$ perf record -e '{cpu/mem-loads-aux/S,cpu/mem-loads,ldlat=3/PS}' -- ls

Opening the event "cpu/mem-loads,ldlat=3/PS" returns EINVAL when
precise_ip == 3. It then sets attr.inherit = false, which triggers a
kernel check failure since it doesn't match the group leader's inherit
attribute. As a result, it continues to fail even after precise_ip is
reduced.

By moving the precise_ip fallback earlier, this issue is resolved, as
well as the kernel test robot report mentioned in commit
c33aea446bf555ab.

No negative side effects are expected, because the precise_ip level is
restored by evsel__precise_ip_fallback() if the fallback does not help.

This also aligns with commit 2b70702917337a8d ("perf tools: Remove
evsel__handle_error_quirks()").

Fixes: af954f76eea56453 ("perf tools: Check fallback error and order")
Fixes: c33aea446bf555ab ("perf tools: Fix precise_ip fallback logic")
Reviewed-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Signed-off-by: Zide Chen <zide.chen@...el.com>
---
 tools/perf/util/evsel.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ca74514c8707..6ce32533a213 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2714,12 +2714,12 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
 		goto retry_open;

+	if (evsel__precise_ip_fallback(evsel))
+		goto retry_open;
+
 	if (err == -EINVAL && evsel__detect_missing_features(evsel, cpu))
 		goto fallback_missing_features;

-	if (evsel__precise_ip_fallback(evsel))
-		goto retry_open;
-
 out_close:
 	if (err)
 		threads->err_thread = thread;
-- 
2.51.0