Added VALGRIND_YIELD to be able to abort from busy loops

Valgrind is single threaded and only changes threads as part of
system calls or waits.

I found some busy loops where the server assumes that some other
thread will change the state, which will not happen with valgrind.

Added VALGRIND_YIELD to the loops, which calls pthread_yield() if
HAVE_VALGRIND is defined.

Added pthread_yield() to the loops in table_cache.

We should consider changing some of the VALGRIND_YIELD calls to call
pthread_yield() as busy loop without any sleep() is usually a bad
thing.

Reviewer: [email protected]

Author: montywi

include/my_valgrind.h

@@ -42,6 +42,7 @@
 # else
 #  define MSAN_STAT_WORKAROUND(st) ((void) 0)
 # endif
+# define VALGRIND_YIELD
 #elif defined(HAVE_VALGRIND_MEMCHECK_H) && defined(HAVE_valgrind)
 # include <valgrind/memcheck.h>
 # define HAVE_MEM_CHECK
@@ -55,6 +56,7 @@
 # define MEM_SET_VBITS(a,b,len) VALGRIND_SET_VBITS(a,b,len)
 # define REDZONE_SIZE 8
 # define MSAN_STAT_WORKAROUND(st) ((void) 0)
+# define VALGRIND_YIELD pthread_yield()
 #elif defined(__SANITIZE_ADDRESS__) && (!defined(_MSC_VER) || defined (__clang__))
 # include <sanitizer/asan_interface.h>
 /* How to do manual poisoning:
@@ -70,6 +72,7 @@
 # define MEM_SET_VBITS(a,b,len) ((void) 0)
 # define MSAN_STAT_WORKAROUND(st) ((void) 0)
 # define REDZONE_SIZE 8
+# define VALGRIND_YIELD
 #else
 # define MEM_UNDEFINED(a,len) ((void) 0)
 # define MEM_MAKE_ADDRESSABLE(a,len) ((void) 0)
@@ -81,6 +84,7 @@
 # define MEM_SET_VBITS(a,b,len) ((void) 0)
 # define REDZONE_SIZE 0
 # define MSAN_STAT_WORKAROUND(st) ((void) 0)
+# define VALGRIND_YIELD
 #endif /* __has_feature(memory_sanitizer) */
 
 #ifdef TRASH_FREED_MEMORY

sql/sql_base.cc

@@ -4690,6 +4690,7 @@ bool open_tables(THD *thd, const DDL_options_st &options,
             goto error;
 
           error= FALSE;
+          pthread_yield();
           goto restart;
         }
         goto error;
@@ -4755,6 +4756,7 @@ bool open_tables(THD *thd, const DDL_options_st &options,
 
             error= FALSE;
             sroutine_to_open= &thd->lex->sroutines_list.first;
+            pthread_yield();
             goto restart;
           }
           /*

sql/table_cache.cc

@@ -901,6 +901,7 @@ TABLE_SHARE *tdc_acquire_share(THD *thd, TABLE_LIST *tl, uint flags,
   {
     mysql_mutex_unlock(&element->LOCK_table_share);
     lf_hash_search_unpin(thd->tdc_hash_pins);
+    VALGRIND_YIELD;
     goto retry;
   }
   lf_hash_search_unpin(thd->tdc_hash_pins);

storage/innobase/trx/trx0purge.cc

@@ -1177,6 +1177,7 @@ dict_table_t *purge_sys_t::close_and_reopen(table_id_t id, THD *thd,
   MDL_context *mdl_context= static_cast<MDL_context*>(thd_mdl_context(thd));
   ut_ad(mdl_context);
  retry:
+  VALGRIND_YIELD;
   ut_ad(m_active);
 
   for (que_thr_t *thr= UT_LIST_GET_FIRST(purge_sys.query->thrs); thr;