[PATCH v2] perf ui/tui: Fix possible UI rendering breakage

[Namhyung Kim]

The tui_helpline__push() should acquire/release the ui__lock when it
deals with screen setting.  Otherwise it could race with display thread
and screen rendering would not be handled properly.

Also move helpline__push/pop out of ui__lock to prevent deadlock.

Fixes: e6e904687949 ("perf ui: Introduce struct ui_helpline")
Signed-off-by: Namhyung Kim <namhy...@kernel.org>
---
 tools/perf/ui/browser.c      |  7 ++++---
 tools/perf/ui/tui/helpline.c | 17 ++++++++++++-----
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/tools/perf/ui/browser.c b/tools/perf/ui/browser.c
index 4f75561424ed..2a99a0fbbcf6 100644
--- a/tools/perf/ui/browser.c
+++ b/tools/perf/ui/browser.c
@@ -294,16 +294,17 @@ int ui_browser__show(struct ui_browser *browser, const 
char *title,
        va_start(ap, helpline);
        err = vasprintf(&browser->helpline, helpline, ap);
        va_end(ap);
-       if (err > 0)
-               ui_helpline__push(browser->helpline);
        pthread_mutex_unlock(&ui__lock);
+
+       if (err > 0)
+               ui_helpline__push(helpline);
        return err ? 0 : -1;
 }
 
 void ui_browser__hide(struct ui_browser *browser)
 {
-       pthread_mutex_lock(&ui__lock);
        ui_helpline__pop();
+       pthread_mutex_lock(&ui__lock);
        zfree(&browser->helpline);
        pthread_mutex_unlock(&ui__lock);
 }
diff --git a/tools/perf/ui/tui/helpline.c b/tools/perf/ui/tui/helpline.c
index 4ca799aadb4e..83b6eebb451a 100644
--- a/tools/perf/ui/tui/helpline.c
+++ b/tools/perf/ui/tui/helpline.c
@@ -12,6 +12,14 @@
 char ui_helpline__last_msg[1024];
 bool tui_helpline__set;
 
+static void tui_helpline__puts(const char *msg)
+{
+       SLsmg_gotorc(SLtt_Screen_Rows - 1, 0);
+       SLsmg_set_color(0);
+       SLsmg_write_nstring((char *)msg, SLtt_Screen_Cols);
+       SLsmg_refresh();
+}
+
 static void tui_helpline__pop(void)
 {
 }
@@ -20,11 +28,10 @@ static void tui_helpline__push(const char *msg)
 {
        const size_t sz = sizeof(ui_helpline__current);
 
-       SLsmg_gotorc(SLtt_Screen_Rows - 1, 0);
-       SLsmg_set_color(0);
-       SLsmg_write_nstring((char *)msg, SLtt_Screen_Cols);
-       SLsmg_refresh();
+       pthread_mutex_lock(&ui__lock);
        strncpy(ui_helpline__current, msg, sz)[sz - 1] = '\0';
+       tui_helpline__puts(msg);
+       pthread_mutex_unlock(&ui__lock);
 }
 
 static int tui_helpline__show(const char *format, va_list ap)
@@ -40,7 +47,7 @@ static int tui_helpline__show(const char *format, va_list ap)
        tui_helpline__set = true;
 
        if (ui_helpline__last_msg[backlog - 1] == '\n') {
-               ui_helpline__puts(ui_helpline__last_msg);
+               tui_helpline__puts(ui_helpline__last_msg);
                SLsmg_refresh();
                backlog = 0;
        }
-- 
2.19.0