perf hists browser: Invalidate ui_browser->top after timer calls

With underlying dynamic data structures we need to invalidate pointers
to them after a timer, as that entry may have vanished (decayed in top,
for instance).

I forgot about browser_ui->top. Fix it by resetting it to null after a
timer. The seek operation from SEEK_SET will then set it to a valid
entry because it starts from rb_first(&hists->entries).

Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-2ssjm0ouh9tsz4dwkcu7c40n@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 14 insertions, 2 deletions

diff --git a/tools/perf/util/ui/browser.c b/tools/perf/util/ui/browser.c
index 2923c493fb6a..078ceaf5f8c1 100644
--- a/tools/perf/util/ui/browser.c
+++ b/tools/perf/util/ui/browser.c
@@ -249,6 +249,7 @@ void ui_browser__update_nr_entries(struct ui_browser *browser, u32 nr_entries)
                 browser->top_idx += offset;
         }
 
+        browser->top = NULL;
         browser->seek(browser, browser->top_idx, SEEK_SET);
 }
 
diff --git a/tools/perf/util/ui/browsers/hists.c b/tools/perf/util/ui/browsers/hists.c
index 4a3a7c96b9b6..b144b108029a 100644
--- a/tools/perf/util/ui/browsers/hists.c
+++ b/tools/perf/util/ui/browsers/hists.c
@@ -600,14 +600,23 @@ static int hist_browser__show_entry(struct hist_browser *self,
         return printed;
 }
 
+static void ui_browser__hists_init_top(struct ui_browser *browser)
+{
+        if (browser->top == NULL) {
+                struct hist_browser *hb;
+
+                hb = container_of(browser, struct hist_browser, b);
+                browser->top = rb_first(&hb->hists->entries);
+        }
+}
+
 static unsigned int hist_browser__refresh(struct ui_browser *self)
 {
         unsigned row = 0;
         struct rb_node *nd;
         struct hist_browser *hb = container_of(self, struct hist_browser, b);
 
-        if (self->top == NULL)
-                self->top = rb_first(&hb->hists->entries);
+        ui_browser__hists_init_top(self);
 
         for (nd = self->top; nd; nd = rb_next(nd)) {
                 struct hist_entry *h = rb_entry(nd, struct hist_entry, rb_node);
@@ -659,6 +668,8 @@ static void ui_browser__hists_seek(struct ui_browser *self,
         if (self->nr_entries == 0)
                 return;
 
+        ui_browser__hists_init_top(self);
+
         switch (whence) {
         case SEEK_SET:
                 nd = hists__filter_entries(rb_first(self->entries));