bzr commit into mysql-5.5 branch (davi:3236) Bug#42054

[Davi Arnaut]

# At a local mysql-5.5 repository of davi

 3236 Davi Arnaut	2011-01-11
      Bug#42054: SELECT CURDATE() is returning bad value
      
      The problem from a user point of view was that on Solaris the
      time related functions (e.g. NOW(), SYSDATE(), etc) would always
      return a fixed time.
      
      This bug was happening due to a logic in the time retrieving
      wrapper function which would only call the time() function every
      half second. This interval between calls would be calculated
      using the gethrtime() and the logic relied on the fact that time
      returned by it is monotonic.
      
      Unfortunately, due to bugs in the gethrtime() implementation,
      there are some cases where the time returned by it can drift
      (See Solaris bug id 6600939), potentially causing the interval
      calculation logic to fail.
      
      Since newer versions of Solaris (10+) have alleviated the
      performance degradation associated with time(2), the solution is
      to simply directly rely on time() at each invocation.
      
      This simplification has an upside that it allows us to eliminate
      a lock which was used to control access to the variables used
      to track the half second interval, thus improving the overall
      scalability of timekeeping related functions (e.g. NOW()).
      
      In spite of the the aforementioned problem, gethrtime() is still
      used in a few places where we need a high resolution but under
      which drifts don't pose a problem.
     @ mysys/my_getsystime.c
        Use time() even if gethrtime() is available. Remove logic which
        relied on gethrtime() to only call time() every half second.
     @ mysys/my_thr_init.c
        Remove mutex which is no longer used.
     @ mysys/mysys_priv.h
        Remove mutex which is no longer used.

    modified:
      mysql-test/suite/perfschema/r/server_init.result
      mysql-test/suite/perfschema/t/server_init.test
      mysys/my_getsystime.c
      mysys/my_init.c
      mysys/my_thr_init.c
      mysys/mysys_priv.h
=== modified file 'mysql-test/suite/perfschema/r/server_init.result'
--- a/mysql-test/suite/perfschema/r/server_init.result	2010-11-12 11:23:17 +0000
+++ b/mysql-test/suite/perfschema/r/server_init.result	2011-01-11 14:02:38 +0000
@@ -31,10 +31,6 @@ select count(name) from mutex_instances
 where name like "wait/synch/mutex/mysys/THR_LOCK_charset";
 count(name)
 1
-select count(name) from mutex_instances
-where name like "wait/synch/mutex/mysys/THR_LOCK_time";
-count(name)
-1
 select count(name) from cond_instances
 where name like "wait/synch/cond/mysys/THR_COND_threads";
 count(name)

=== modified file 'mysql-test/suite/perfschema/t/server_init.test'
--- a/mysql-test/suite/perfschema/t/server_init.test	2010-11-12 11:23:17 +0000
+++ b/mysql-test/suite/perfschema/t/server_init.test	2011-01-11 14:02:38 +0000
@@ -52,9 +52,6 @@ select count(name) from mutex_instances
 select count(name) from mutex_instances
  where name like "wait/synch/mutex/mysys/THR_LOCK_charset";
 
-select count(name) from mutex_instances
- where name like "wait/synch/mutex/mysys/THR_LOCK_time";
-
 # There are no global rwlock in mysys
 
 # Verify that these global conditions have been properly initilized in mysys

=== modified file 'mysys/my_getsystime.c'
--- a/mysys/my_getsystime.c	2011-01-11 13:53:50 +0000
+++ b/mysys/my_getsystime.c	2011-01-11 14:02:38 +0000
@@ -62,10 +62,6 @@ ulonglong my_getsystime()
 time_t my_time(myf flags __attribute__((unused)))
 {
   time_t t;
-#ifdef HAVE_GETHRTIME
-  (void) my_micro_time_and_time(&t);
-  return t;
-#else
   /* The following loop is here beacuse time() may fail on some systems */
   while ((t= time(0)) == (time_t) -1)
   {
@@ -73,7 +69,6 @@ time_t my_time(myf flags __attribute__((
       fprintf(stderr, "%s: Warning: time() call failed\n", my_progname);
   }
   return t;
-#endif
 }
 
 
@@ -154,31 +149,6 @@ ulonglong my_micro_time_and_time(time_t
   GetSystemTimeAsFileTime((FILETIME*)&newtime);
   *time_arg= (time_t) ((newtime - OFFSET_TO_EPOCH) / 10000000);
   return (newtime/10);
-#elif defined(HAVE_GETHRTIME)
-  /*
-    Solaris has a very slow time() call. We optimize this by using the very
-    fast gethrtime() call and only calling time() every 1/2 second
-  */
-  static hrtime_t prev_gethrtime= 0;
-  static time_t cur_time= 0;
-  hrtime_t cur_gethrtime;
-
-  mysql_mutex_lock(&THR_LOCK_time);
-  cur_gethrtime= gethrtime();
-  /*
-    Due to bugs in the Solaris (x86) implementation of gethrtime(),
-    the time returned by it might not be monotonic. Don't use the
-    cached time(2) value if this is a case.
-  */
-  if ((prev_gethrtime > cur_gethrtime) ||
-      ((cur_gethrtime - prev_gethrtime) > DELTA_FOR_SECONDS))
-  {
-    cur_time= time(0);
-    prev_gethrtime= cur_gethrtime;
-  }
-  *time_arg= cur_time;
-  mysql_mutex_unlock(&THR_LOCK_time);
-  return cur_gethrtime/1000;
 #else
   ulonglong newtime;
   struct timeval t;

=== modified file 'mysys/my_init.c'
--- a/mysys/my_init.c	2011-01-11 09:07:37 +0000
+++ b/mysys/my_init.c	2011-01-11 14:02:38 +0000
@@ -510,7 +510,7 @@ PSI_mutex_key key_BITMAP_mutex, key_IO_C
   key_my_thread_var_mutex, key_THR_LOCK_charset, key_THR_LOCK_heap,
   key_THR_LOCK_isam, key_THR_LOCK_lock, key_THR_LOCK_malloc,
   key_THR_LOCK_mutex, key_THR_LOCK_myisam, key_THR_LOCK_net,
-  key_THR_LOCK_open, key_THR_LOCK_threads, key_THR_LOCK_time,
+  key_THR_LOCK_open, key_THR_LOCK_threads,
   key_TMPDIR_mutex, key_THR_LOCK_myisam_mmap;
 
 static PSI_mutex_info all_mysys_mutexes[]=
@@ -540,7 +540,6 @@ static PSI_mutex_info all_mysys_mutexes[
   { &key_THR_LOCK_net, "THR_LOCK_net", PSI_FLAG_GLOBAL},
   { &key_THR_LOCK_open, "THR_LOCK_open", PSI_FLAG_GLOBAL},
   { &key_THR_LOCK_threads, "THR_LOCK_threads", PSI_FLAG_GLOBAL},
-  { &key_THR_LOCK_time, "THR_LOCK_time", PSI_FLAG_GLOBAL},
   { &key_TMPDIR_mutex, "TMPDIR_mutex", PSI_FLAG_GLOBAL},
   { &key_THR_LOCK_myisam_mmap, "THR_LOCK_myisam_mmap", PSI_FLAG_GLOBAL}
 };

=== modified file 'mysys/my_thr_init.c'
--- a/mysys/my_thr_init.c	2011-01-11 09:07:37 +0000
+++ b/mysys/my_thr_init.c	2011-01-11 14:02:38 +0000
@@ -25,7 +25,7 @@
 pthread_key(struct st_my_thread_var*, THR_KEY_mysys);
 mysql_mutex_t THR_LOCK_malloc, THR_LOCK_open,
               THR_LOCK_lock, THR_LOCK_isam, THR_LOCK_myisam, THR_LOCK_heap,
-              THR_LOCK_net, THR_LOCK_charset, THR_LOCK_threads, THR_LOCK_time,
+              THR_LOCK_net, THR_LOCK_charset, THR_LOCK_threads,
               THR_LOCK_myisam_mmap;
 
 mysql_cond_t  THR_COND_threads;
@@ -219,7 +219,6 @@ my_bool my_thread_global_init(void)
   mysql_mutex_init(key_THR_LOCK_myisam_mmap, &THR_LOCK_myisam_mmap, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_THR_LOCK_heap, &THR_LOCK_heap, MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_THR_LOCK_net, &THR_LOCK_net, MY_MUTEX_INIT_FAST);
-  mysql_mutex_init(key_THR_LOCK_time, &THR_LOCK_time, MY_MUTEX_INIT_FAST);
   mysql_cond_init(key_THR_COND_threads, &THR_COND_threads, NULL);
 
 #if !defined(HAVE_LOCALTIME_R) || !defined(HAVE_GMTIME_R)
@@ -288,7 +287,6 @@ void my_thread_global_end(void)
   mysql_mutex_destroy(&THR_LOCK_myisam_mmap);
   mysql_mutex_destroy(&THR_LOCK_heap);
   mysql_mutex_destroy(&THR_LOCK_net);
-  mysql_mutex_destroy(&THR_LOCK_time);
   mysql_mutex_destroy(&THR_LOCK_charset);
   if (all_threads_killed)
   {

=== modified file 'mysys/mysys_priv.h'
--- a/mysys/mysys_priv.h	2011-01-11 09:07:37 +0000
+++ b/mysys/mysys_priv.h	2011-01-11 14:02:38 +0000
@@ -45,7 +45,7 @@ extern PSI_mutex_key key_BITMAP_mutex, k
   key_my_thread_var_mutex, key_THR_LOCK_charset, key_THR_LOCK_heap,
   key_THR_LOCK_isam, key_THR_LOCK_lock, key_THR_LOCK_malloc,
   key_THR_LOCK_mutex, key_THR_LOCK_myisam, key_THR_LOCK_net,
-  key_THR_LOCK_open, key_THR_LOCK_threads, key_THR_LOCK_time,
+  key_THR_LOCK_open, key_THR_LOCK_threads,
   key_TMPDIR_mutex, key_THR_LOCK_myisam_mmap;
 
 extern PSI_cond_key key_COND_alarm, key_IO_CACHE_SHARE_cond,
@@ -60,7 +60,7 @@ extern PSI_thread_key key_thread_alarm;
 
 extern mysql_mutex_t THR_LOCK_malloc, THR_LOCK_open, THR_LOCK_keycache;
 extern mysql_mutex_t THR_LOCK_lock, THR_LOCK_isam, THR_LOCK_net;
-extern mysql_mutex_t THR_LOCK_charset, THR_LOCK_time;
+extern mysql_mutex_t THR_LOCK_charset;
 
 #include <mysql/psi/mysql_file.h>
 


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