rare/interrupts-graph.py: thread for data retrieval

This fixes wrong data updates when the UI gets paused (and as a result,
the data update gets delayed).

1 files changed, 32 insertions, 4 deletions

diff --git a/rare/interrupts-graph.py b/rare/interrupts-graph.py
index dce9316..6e4ee23 100755
--- a/rare/interrupts-graph.py
+++ b/rare/interrupts-graph.py
@@ -6,14 +6,13 @@
 # Wishlist:
 # Thicker legend lines
 # Nicier smoothing
-# split rendering thread from IO thread (otherwise the data is retrieved too
-# late when dragging the legend box)
 
 import matplotlib.pyplot as plt
 import matplotlib
 from collections import deque, OrderedDict
 import numpy as np
 from scipy.interpolate import spline, interp1d
+import threading
 
 # Maximimum number of time units to keep
 XSCALE = 60
@@ -56,6 +55,16 @@ def is_line_ok(name, yvalues):
 # Fix Unicode font
 matplotlib.rc('font', family='DejaVu Sans')
 
+# From http://stackoverflow.com/a/490090
+def synchronized(lock):
+    """Synchronization decorator."""
+    def wrap(f):
+        def newFunction(*args, **kw):
+            with lock:
+                return f(*args, **kw)
+        return newFunction
+    return wrap
+
 def get_numbers():
     # TODO: may break the graph if a line disappears
     with open('/proc/interrupts') as pi:
@@ -144,14 +153,22 @@ def update_title():
         title += ' (paused - press Space to resume)'
     plt.gcf().canvas.set_window_title(title)
 
+# Lock to avoid updating the UI while the data is being refreshed
+data_lock = threading.Lock()
+@synchronized(data_lock)
+def refresh_data():
+    # Update data
+    for name, n in get_diffs():
+        yvalues[name].append(n)
+
 smooth = {}
+@synchronized(data_lock)
 def update():
     """Reads new data and updates the line values."""
     global update_legend
-    # Update data
+    # Update lines
     for name, n in get_diffs():
         ys = yvalues[name]
-        ys.append(n)
         # Consider only strictly positive values
         ydata = [y for y in ys if y > 0]
         xdata = [i for i, y in enumerate(ys) if y > 0]
@@ -232,8 +249,19 @@ def do_draw():
 
 update_title()
 
+# Separate worker for fetching data
+def refresh_data_timer():
+    global t
+    t = threading.Timer(INTERVAL, refresh_data_timer)
+    t.start()
+    refresh_data()
+refresh_data_timer()
+
 while running:
     if not paused:
         update()
     do_draw()
     plt.pause(INTERVAL)
+
+# Cancel any scheduled timer
+t.cancel()