Bug#27198: Error returns from time() are ignored

gettimeofday() can fail and presumably, so can time().
Keep an eye on it.

Since we have no data on this at all so far, we just
retry on failure (and log the event), assuming that
this is just an intermittant failure. This might of
course hang the threat until we succeed. Once we know
more about these failures, an appropriate more clever
scheme may be picked (only try so many times per thread,
etc., if that fails, return last "good" time() we got or
some such).  Using sql_print_information() to log as this
probably only occurs in high load scenarios where the debug-
trace likely is disabled (or might interfere with testing
the effect).  No test-case as this is a non-deterministic
issue.

sql/mysql_priv.h

@@ -302,6 +302,14 @@ inline THD *_current_thd(void)
 }
 #define current_thd _current_thd()
 
+/* log.cc */
+void sql_perror(const char *message);
+
+void vprint_msg_to_log( enum loglevel level, const char *format, va_list args );
+void sql_print_error( const char *format, ... );
+void sql_print_warning( const char *format, ...); 
+void sql_print_information( const char *format, ...); 
+
 #include "sql_string.h"
 #include "sql_list.h"
 #include "sql_map.h"
@@ -657,15 +665,6 @@ void key_unpack(String *to,TABLE *form,uint index);
 bool check_if_key_used(TABLE *table, uint idx, List<Item> &fields);
 void init_errmessage(void);
 
-void sql_perror(const char *message);
-
-void vprint_msg_to_log( enum loglevel level, const char *format, va_list args );
-void sql_print_error( const char *format, ... );
-void sql_print_warning( const char *format, ...); 
-void sql_print_information( const char *format, ...); 
-
-
-
 bool fn_format_relative_to_data_home(my_string to, const char *name,
 				     const char *dir, const char *extension);
 bool open_log(MYSQL_LOG *log, const char *hostname,

sql/sql_class.h

@@ -569,17 +569,33 @@ class THD :public ilink
     proc_info = old_msg;
     pthread_mutex_unlock(&mysys_var->mutex);
   }
+
+  static inline void safe_time(time_t *t)
+  {
+    /**
+       Wrapper around time() which retries on error (-1)
+
+       @details
+       This is needed because, despite the documentation, time() may fail
+       in some circumstances.  Here we retry time() until it succeeds, and
+       log the failure so that performance problems related to this can be
+       identified.
+    */
+    while(unlikely(time(t) == ((time_t) -1)))
+      sql_print_information("time() failed with %d", errno);
+  }
+
   inline time_t query_start() { query_start_used=1; return start_time; }
-  inline void	set_time()    { if (user_time) start_time=time_after_lock=user_time; else time_after_lock=time(&start_time); }
-  inline void	end_time()    { time(&start_time); }
+  inline void	set_time()    { if (user_time) start_time=time_after_lock=user_time; else { safe_time(&start_time); time_after_lock= start_time; }}
+  inline void	end_time()    { safe_time(&start_time); }
   inline void	set_time(time_t t) { time_after_lock=start_time=user_time=t; }
-  inline void	lock_time()   { time(&time_after_lock); }
+  inline void	lock_time()   { safe_time(&time_after_lock); }
   inline void	insert_id(ulonglong id)
   { last_insert_id=id; insert_id_used=1; }
   inline ulonglong insert_id(void)
   {
     if (!last_insert_id_used)
-    {      
+    {
       last_insert_id_used=1;
       current_insert_id=last_insert_id;
     }
@@ -588,7 +604,7 @@ class THD :public ilink
   inline ulonglong found_rows(void)
   {
     return limit_found_rows;
-  }                                                                         
+  }
   inline bool active_transaction()
   {
 #ifdef USING_TRANSACTIONS