perf TUI: Don't ignore job control

In its infinite wisdom, by default, SLang sets susp undef, and this can
only be un-done by calling SLtty_set_suspend_state(true). After every
SLang_init_tty().

Additionally, no provisions are made for maintaining the teletype
attributes across suspend/continue (outside of curses emulation
mode(?!), which provides full support, naturally), so we need to save
and restore the flags ourselves, as well as reset the text colours when
going under. We need to also re-draw the screen, and raising SIGWINCH,
shockingly, Just Works.

The correct solution would be to Not Use SLang, but as a stop-gap,
this makes TUI 'perf report' usable.

Signed-off-by: Ahelenia Ziemiańska <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Tested-by: Namhyung Kim <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: yaowenbin <[e-mail]>
Link: https://lore.kernel.org/r/0354dc[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/ui/browsers/annotate.c

···
 	/* reset abort key so that it can get Ctrl-C as a key */
 	SLang_reset_tty();
 	SLang_init_tty(0, 0, 0);
+	SLtty_set_suspend_state(true);
 
 	return map_symbol__tui_annotate(&he->ms, evsel, hbt);
 }

tools/perf/ui/browsers/hists.c

···
 	/* reset abort key so that it can get Ctrl-C as a key */
 	SLang_reset_tty();
 	SLang_init_tty(0, 0, 0);
+	SLtty_set_suspend_state(true);
 
 	if (min_pcnt)
 		browser->min_pcnt = min_pcnt;
···
 	/* reset abort key so that it can get Ctrl-C as a key */
 	SLang_reset_tty();
 	SLang_init_tty(0, 0, 0);
+	SLtty_set_suspend_state(true);
 
 	memset(&action, 0, sizeof(action));
 

tools/perf/ui/browsers/scripts.c

···
 	printf("\033[c\033[H\033[J");
 	fflush(stdout);
 	SLang_init_tty(0, 0, 0);
+	SLtty_set_suspend_state(true);
 	SLsmg_refresh();
 }
 

tools/perf/ui/tui/setup.c

···
 #include <signal.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <termios.h>
 #include <unistd.h>
 #include <linux/kernel.h>
 #ifdef HAVE_BACKTRACE_SUPPORT
 #include <execinfo.h>
 #endif
 
+#include "../../util/color.h"
 #include "../../util/debug.h"
 #include "../browser.h"
 #include "../helpline.h"
···
 	exit(0);
 }
 
+static void ui__sigcont(int sig)
+{
+	static struct termios tty;
+
+	if (sig == SIGTSTP) {
+		while (tcgetattr(SLang_TT_Read_FD, &tty) == -1 && errno == EINTR)
+			;
+		while (write(SLang_TT_Read_FD, PERF_COLOR_RESET, sizeof(PERF_COLOR_RESET) - 1) == -1 && errno == EINTR)
+			;
+		raise(SIGSTOP);
+	} else {
+		while (tcsetattr(SLang_TT_Read_FD, TCSADRAIN, &tty) == -1 && errno == EINTR)
+			;
+		raise(SIGWINCH);
+	}
+}
+
 int ui__init(void)
 {
 	int err;
···
 	err = SLang_init_tty(-1, 0, 0);
 	if (err < 0)
 		goto out;
+	SLtty_set_suspend_state(true);
 
 	err = SLkp_init();
 	if (err < 0) {
···
 	signal(SIGINT, ui__signal);
 	signal(SIGQUIT, ui__signal);
 	signal(SIGTERM, ui__signal);
+	signal(SIGTSTP, ui__sigcont);
+	signal(SIGCONT, ui__sigcont);
 
 	perf_error__register(&perf_tui_eops);