From d30f2d869b6a2e985351867424037eb7bcb57386 Mon Sep 17 00:00:00 2001 From: Hongfu Li Date: Mon, 13 Jul 2026 17:36:26 +0800 Subject: [PATCH] perf doc: Fix mmap failure checks in topdown example Use MAP_FAILED instead of NULL to detect mmap errors, and fix the slots_p variable name typo in the sample code. Signed-off-by: Hongfu Li Signed-off-by: Namhyung Kim --- tools/perf/Documentation/topdown.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/Documentation/topdown.txt b/tools/perf/Documentation/topdown.txt index 5c17fff694ee..fd4214f9a7b0 100644 --- a/tools/perf/Documentation/topdown.txt +++ b/tools/perf/Documentation/topdown.txt @@ -87,7 +87,7 @@ if (slots_fd < 0) /* Memory mapping the fd permits _rdpmc calls from userspace */ void *slots_p = mmap(0, getpagesize(), PROT_READ, MAP_SHARED, slots_fd, 0); -if (!slot_p) +if (slots_p == MAP_FAILED) .... error ... /* @@ -107,7 +107,7 @@ if (metrics_fd < 0) /* Memory mapping the fd permits _rdpmc calls from userspace */ void *metrics_p = mmap(0, getpagesize(), PROT_READ, MAP_SHARED, metrics_fd, 0); -if (!metrics_p) +if (metrics_p == MAP_FAILED) ... error ... Note: the file descriptors returned by the perf_event_open calls must be memory