linux-kernel - [PATCH 2/3] perf map: Remove kernel map before updating start and end addresses

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Date: Tue,  9 Apr 2024 09:47:38 +0100
From: James Clark <james.clark@....com>
To: linux-perf-users@...r.kernel.org,
	irogers@...gle.com
Cc: James Clark <james.clark@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
	Leo Yan <leo.yan@...ux.dev>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] perf map: Remove kernel map before updating start and end addresses

In a debug build there is validation that mmap lists are sorted when
taking a lock. In machine__update_kernel_mmap() the start and end
addresses are updated resulting in an unsorted list before the map is
removed from the list. When the map is removed, the lock is taken which
triggers the validation and the failure:

  $ perf test "object code reading"
  --- start ---
  perf: util/maps.c:88: check_invariants: Assertion `map__start(prev) <= map__start(map)' failed.
  Aborted

Fix it by updating the addresses after removal, but before insertion.
The bug depends on the ordering and type of debug info on the system and
doesn't reproduce everywhere.

Fixes: 659ad3492b91 ("perf maps: Switch from rbtree to lazily sorted array for addresses")
Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/util/machine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 5eb9044bc223..a26c8bea58d0 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1549,8 +1549,8 @@ static int machine__update_kernel_mmap(struct machine *machine,
 	updated = map__get(orig);
 
 	machine->vmlinux_map = updated;
-	machine__set_kernel_mmap(machine, start, end);
 	maps__remove(machine__kernel_maps(machine), orig);
+	machine__set_kernel_mmap(machine, start, end);
 	err = maps__insert(machine__kernel_maps(machine), updated);
 	map__put(orig);
 
-- 
2.34.1