A follow up patch for the fix for Bug#51263 "Deadlock between

transactional SELECT and ALTER TABLE ...  REBUILD PARTITION".

Remove unused code - TL_WRITE_ALLOW_READ thr_lock.c lock.






include/thr_lock.h:
  Remove TL_WRITE_ALLOW_READ.
mysys/CMakeLists.txt:
  Add thr_lock test to the list of CMake executables to build.
mysys/thr_lock.c:
  Remove TL_WRITE_ALLOW_READ thr_lock.c lock.
  Consequently, simplify lock compatibility rules.
  Remove unused code.
sql/sql_test.cc:
  Remove TL_WRITE_ALLOW_READ lock.

include/thr_lock.h

@@ -53,12 +53,6 @@ enum thr_lock_type { TL_IGNORE=-1,
 			reading/writing to the table.
 		      */
 		     TL_WRITE_ALLOW_WRITE,
-		     /*
-			Write lock, but allow other threads to read.
-			Used by ALTER TABLE in MySQL to allow readers
-			to use the table until ALTER TABLE is finished.
-		     */
-		     TL_WRITE_ALLOW_READ,
 		     /*
 		       WRITE lock used by concurrent insert. Will allow
 		       READ, if one could use concurrent insert on table.

mysys/CMakeLists.txt

@@ -66,3 +66,7 @@ ADD_CONVENIENCE_LIBRARY(mysys ${MYSYS_SOURCES})
 TARGET_LINK_LIBRARIES(mysys dbug strings ${ZLIB_LIBRARY} 
  ${LIBNSL} ${LIBM} ${LIBRT})
 DTRACE_INSTRUMENT(mysys)
+
+ADD_EXECUTABLE(thr_lock thr_lock.c)
+TARGET_LINK_LIBRARIES(thr_lock mysys)
+SET_TARGET_PROPERTIES(thr_lock PROPERTIES COMPILE_FLAGS "-DMAIN")

sql/sql_test.cc

@@ -45,7 +45,6 @@ static const char *lock_descriptions[] =
   /* TL_READ_HIGH_PRIORITY      */  "High priority read lock",
   /* TL_READ_NO_INSERT          */  "Read lock without concurrent inserts",
   /* TL_WRITE_ALLOW_WRITE       */  "Write lock that allows other writers",
-  /* TL_WRITE_ALLOW_READ        */  "Write lock, but allow reading",
   /* TL_WRITE_CONCURRENT_INSERT */  "Concurrent insert lock",
   /* TL_WRITE_DELAYED           */  "Lock used by delayed insert",
   /* TL_WRITE_DEFAULT           */  NULL,