---

yaml
---
r: 48561
b: refs/heads/master
c: 41cf544
h: refs/heads/master
i:
  48559: 024e398
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8b9365d753d9870bb6451504c13570b81923228f
+refs/heads/master: 41cf54455da5e5dc847a9733d49ca23b5e7dd59e

trunk/kernel/time.c

@@ -500,15 +500,56 @@ unsigned int jiffies_to_usecs(const unsigned long j)
 }
 EXPORT_SYMBOL(jiffies_to_usecs);
 
+/*
+ * When we convert to jiffies then we interpret incoming values
+ * the following way:
+ *
+ * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
+ *
+ * - 'too large' values [that would result in larger than
+ *   MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
+ *
+ * - all other values are converted to jiffies by either multiplying
+ *   the input value by a factor or dividing it with a factor
+ *
+ * We must also be careful about 32-bit overflows.
+ */
 unsigned long msecs_to_jiffies(const unsigned int m)
 {
-	if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+	/*
+	 * Negative value, means infinite timeout:
+	 */
+	if ((int)m < 0)
 		return MAX_JIFFY_OFFSET;
+
 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
+	/*
+	 * HZ is equal to or smaller than 1000, and 1000 is a nice
+	 * round multiple of HZ, divide with the factor between them,
+	 * but round upwards:
+	 */
 	return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
+	/*
+	 * HZ is larger than 1000, and HZ is a nice round multiple of
+	 * 1000 - simply multiply with the factor between them.
+	 *
+	 * But first make sure the multiplication result cannot
+	 * overflow:
+	 */
+	if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+		return MAX_JIFFY_OFFSET;
+
 	return m * (HZ / MSEC_PER_SEC);
 #else
+	/*
+	 * Generic case - multiply, round and divide. But first
+	 * check that if we are doing a net multiplication, that
+	 * we wouldnt overflow:
+	 */
+	if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+		return MAX_JIFFY_OFFSET;
+
 	return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
 #endif
 }