perf top: Fix stdio interface input handling with glibc 2.28+

commit 29b4f5f188571c112713c35cc87eefb46efee612 upstream.

Since glibc 2.28 when running 'perf top --stdio', input handling no
longer works, but hitting any key always just prints the "Mapped keys"
help text.

To fix it, call clearerr() in the display_thread() loop to clear any EOF
sticky errors, as instructed in the glibc NEWS file
(https://sourceware.org/git/?p=glibc.git;a=blob;f=NEWS):

 * All stdio functions now treat end-of-file as a sticky condition.  If you
   read from a file until EOF, and then the file is enlarged by another
   process, you must call clearerr or another function with the same effect
   (e.g. fseek, rewind) before you can read the additional data.  This
   corrects a longstanding C99 conformance bug.  It is most likely to affect
   programs that use stdio to read interactive input from a terminal.
   (Bug #1190.)

Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200305083714.9381-2-tommi.t.rantala@nokia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index cd2900ac473fc602654575929689026712714036..280448114add1ea19f52048d8a802a654d0b34fd 100644 (file)
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -633,7 +633,9 @@ repeat:
        delay_msecs = top->delay_secs * MSEC_PER_SEC;
        set_term_quiet_input(&save);
        /* trash return*/
-       getc(stdin);
+       clearerr(stdin);
+       if (poll(&stdin_poll, 1, 0) > 0)
+               getc(stdin);
 
        while (!done) {
                perf_top__print_sym_table(top);