The function cRingBufferLinear::Clear() can now be called safely from the reading thread, without additional locking

HISTORY

@@ -8882,7 +8882,7 @@ Video Disk Recorder Revision History
 - Added a short sleep to cTSBuffer::Action() to avoid high CPU usage (thanks to
   Sergey Chernyavskiy).
 
-2017-03-18: Version 2.3.3
+2017-03-19: Version 2.3.3
 
 - Added 'S3W ABS-3A' to sources.conf (thanks to Frank Richter).
 - Fixed a possible deadlock in the recordings handler thread.
@@ -8918,3 +8918,5 @@ Video Disk Recorder Revision History
   that is capable of decrypting more than one channel ("Multi Channel Decryption")
   to decrypt channels from different transponders. See the remarks in mtd.h on
   what a derived cCamSlot class needs to do in order to activate MTD.
+- The function cRingBufferLinear::Clear() can now be called safely from the
+  reading thread, without additional locking.

ringbuffer.c

@@ -7,7 +7,7 @@
  * Parts of this file were inspired by the 'ringbuffy.c' from the
  * LinuxDVB driver (see linuxtv.org).
  *
- * $Id: ringbuffer.c 4.1 2016/12/22 10:26:13 kls Exp $
+ * $Id: ringbuffer.c 4.2 2017/03/19 12:43:36 kls Exp $
  */
 
 #include "ringbuffer.h"
@@ -216,9 +216,10 @@ int cRingBufferLinear::Available(void)
 
 void cRingBufferLinear::Clear(void)
 {
-  tail = head = margin;
+  int Head = head;
+  tail = Head;
 #ifdef DEBUGRINGBUFFERS
-  lastHead = head;
+  lastHead = Head;
   lastTail = tail;
   lastPut = lastGet = -1;
 #endif

ringbuffer.h

@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: ringbuffer.h 4.1 2016/12/22 10:26:13 kls Exp $
+ * $Id: ringbuffer.h 4.2 2017/03/19 13:11:39 kls Exp $
  */
 
 #ifndef __RINGBUFFER_H
@@ -80,6 +80,8 @@ public:
   virtual int Free(void) { return Size() - Available() - 1 - margin; }
   virtual void Clear(void);
     ///< Immediately clears the ring buffer.
+    ///< This function may safely be called from the reading thread without additional
+    ///< locking. If called from the writing thread, proper locking must be used.
   int Read(int FileHandle, int Max = 0);
     ///< Reads at most Max bytes from FileHandle and stores them in the
     ///< ring buffer. If Max is 0, reads as many bytes as possible.