From 40bf1cb07ee72480dd831d7a13e42728dfad35e2 Mon Sep 17 00:00:00 2001
From: Changbin Du <changbin.du@huawei.com>
Date: Sat, 13 May 2023 15:40:00 +0800
Subject: [PATCH] perf ftrace: Flush output after each writing

The pager will result stdout in full buffering mode instead of line
buffering. We need to make the trace visible timely.

Signed-off-by: Changbin Du <changbin.du@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230513074000.733550-1-changbin.du@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/builtin-ftrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 810e3376c7d6..ad2a9ae041f6 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -650,6 +650,8 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
 				break;
 			if (fwrite(buf, n, 1, stdout) != 1)
 				break;
+			/* flush output since stdout is in full buffering mode due to pager */
+			fflush(stdout);
 		}
 	}