Added backtrace functions for debugging

HISTORY

@@ -9058,11 +9058,21 @@ Video Disk Recorder Revision History
 
 2017-05-31: Version 2.3.6
 
-- Added debug output for checking the correct sequence of locking global lists
-  (with help and suggestions from Jasmin Jessich). To activate this, define the
-  macro DEBUG_LOCKSEQ in thread.c. At the first occurrence of an invalid locking
-  sequence, the 20 most recent locks will be printed to stderr, followed by a
-  backtrace that led to the call in question.
+- Added backtrace functions for debugging (see cBackTrace in thread.h).
+- Added checking the correct sequence of locking global lists (with help and
+  suggestions from Jasmin Jessich). At the first occurrence of an invalid locking
+  sequence, the 20 most recent locks will be written to the log file, followed by a
+  backtrace that led to the call in question. This code can be activated by defining
+  the macro DEBUG_LOCKSEQ in thread.c (which is on by default).
+  When debugging an actual invalid locking sequence, you can additionally define
+  the macro DEBUG_LOCKCALL in thread.c, which will add information about the caller
+  of each lock. Note that this may cause some stress on the CPU, therefore it is off
+  by default.
+- The file Make.config.template now reacts on DEBUG=1 in the 'make' command line,
+  and disables code optimizations by setting -O0 (thanks to Jasmin Jessich).
+  This can be helpful when backtracing highly optimized code. You may want to
+  'make distclean' before running 'make' with a modified setting of DEBUG, to make
+  sure all object files are newly compiled.
 - Fixed the locking sequence when dumping EPG data.
 - Fixed the locking sequence when starting a recording.
 - The Makefiles now use the macro $(Q) instead of a plain '@' in front of their