Patch "perf record: Fix "read LOST count failed" msg with sample read" has been added to the 6.3-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    perf record: Fix "read LOST count failed" msg with sample read

to the 6.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-record-fix-read-lost-count-failed-msg-with-samp.patch
and it can be found in the queue-6.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a8190131b0421b1b6d76a17f4f4fc83e2637a8b6
Author: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Date:   Wed Mar 1 07:04:13 2023 -0800

    perf record: Fix "read LOST count failed" msg with sample read
    
    [ Upstream commit 07d85ba9d04e1ebd282f656a29ddf08c5b7b32a2 ]
    
    Hundreds of "read LOST count failed" error messages may be displayed,
    when the below command is launched.
    
    perf record -e '{cpu/mem-loads-aux/,cpu/event=0xcd,umask=0x1/}:S' -a
    
    According to the commit 89e3106fa25fb1b6 ("libperf: Handle read format
    in perf_evsel__read()"), the PERF_FORMAT_GROUP is only available for
    the leader. However, the record__read_lost_samples() goes through every
    entry of an evlist, which includes both leader and member. The member
    event errors out and triggers the error message. Since there may be
    hundreds of CPUs on a server, the message will be printed hundreds of
    times, which is very annoying.
    
    The message itself is correct, but the pr_err is a overkill. Other error
    messages in the record__read_lost_samples() are all pr_debug. To make
    the output format consistent, change the pr_err("read LOST count
    failed\n"); to pr_debug("read LOST count failed\n");.
    User can still get the message via -v option.
    
    Fixes: e3a23261ad06d598 ("perf record: Read and inject LOST_SAMPLES events")
    Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
    Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
    Cc: Ian Rogers <irogers@xxxxxxxxxx>
    Cc: Ingo Molnar <mingo@xxxxxxxxxx>
    Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
    Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
    Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230301150413.27011-1-kan.liang@xxxxxxxxxxxxxxx
    Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 8374117e66f6e..be7c0c29d15b0 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1866,7 +1866,7 @@ static void __record__read_lost_samples(struct record *rec, struct evsel *evsel,
 	int id_hdr_size;
 
 	if (perf_evsel__read(&evsel->core, cpu_idx, thread_idx, &count) < 0) {
-		pr_err("read LOST count failed\n");
+		pr_debug("read LOST count failed\n");
 		return;
 	}