Bug #45225 Locking: hang if drop table with no timeout

This patch introduces timeouts for metadata locks. 

The timeout is specified in seconds using the new dynamic system 
variable  "lock_wait_timeout" which has both GLOBAL and SESSION
scopes. Allowed values range from 1 to 31536000 seconds (= 1 year). 
The default value is 1 year.

The new server parameter "lock-wait-timeout" can be used to set
the default value parameter upon server startup.

"lock_wait_timeout" applies to all statements that use metadata locks.
These include DML and DDL operations on tables, views, stored procedures
and stored functions. They also include LOCK TABLES, FLUSH TABLES WITH
READ LOCK and HANDLER statements.

The patch also changes thr_lock.c code (table data locks used by MyISAM
and other simplistic engines) to use the same system variable.
InnoDB row locks are unaffected.

One exception to the handling of the "lock_wait_timeout" variable
is delayed inserts. All delayed inserts are executed with a timeout
of 1 year regardless of the setting for the global variable. As the
connection issuing the delayed insert gets no notification of 
delayed insert timeouts, we want to avoid unnecessary timeouts.

It's important to note that the timeout value is used for each lock
acquired and that one statement can take more than one lock.
A statement can therefore block for longer than the lock_wait_timeout 
value before reporting a timeout error. When lock timeout occurs, 
ER_LOCK_WAIT_TIMEOUT is reported.

Test case added to lock_multi.test.


include/my_pthread.h:
  Added macros for comparing two timespec structs.
include/thr_lock.h:
  Introduced timeouts for thr_lock.c locks.
mysql-test/r/mysqld--help-notwin.result:
  Updated result file with the new server variable.
mysql-test/r/mysqld--help-win.result:
  Updated result file with the new server variable.
mysql-test/suite/sys_vars/r/lock_wait_timeout_basic.result:
  Added basic test for the new server variable.
mysql-test/suite/sys_vars/t/lock_wait_timeout_basic.test:
  Added basic test for the new server variable.
mysys/thr_lock.c:
  Introduced timeouts for thr_lock.c locks.
sql/mdl.cc:
  Introduced timeouts for metadata locks.
sql/mdl.h:
  Introduced timeouts for metadata locks.
sql/sql_base.cc:
  Introduced timeouts in tdc_wait_for_old_versions().
sql/sql_class.h:
  Added new server variable lock_wait_timeout.
sql/sys_vars.cc:
  Added new server variable lock_wait_timeout.

2 files changed, 48 insertions, 4 deletions

diff --git a/include/my_pthread.h b/include/my_pthread.h
index 343bff6ba72..5402d3929de 100644
--- a/include/my_pthread.h
+++ b/include/my_pthread.h
@@ -102,6 +102,19 @@ struct timespec {
   (ABSTIME).max_timeout_msec= (long)((NSEC)/1000000); \
 }
 
+/**
+   Compare two timespec structs.
+
+   @retval  1 If TS1 ends after TS2.
+
+   @retval  0 If TS1 is equal to TS2.
+
+   @retval -1 If TS1 ends before TS2.
+*/
+#define cmp_timespec(TS1, TS2) \
+  ((TS1.tv.i64 > TS2.tv.i64) ? 1 : \
+   ((TS1.tv.i64 < TS2.tv.i64) ? -1 : 0))
+
 
 int win_pthread_mutex_trylock(pthread_mutex_t *mutex);
 int pthread_create(pthread_t *, const pthread_attr_t *, pthread_handler, void *);
@@ -414,6 +427,33 @@ int my_pthread_mutex_trylock(pthread_mutex_t *mutex);
 #endif /* !set_timespec_nsec */
 #endif /* HAVE_TIMESPEC_TS_SEC */
 
+/**
+   Compare two timespec structs.
+
+   @retval  1 If TS1 ends after TS2.
+
+   @retval  0 If TS1 is equal to TS2.
+
+   @retval -1 If TS1 ends before TS2.
+*/
+#ifdef HAVE_TIMESPEC_TS_SEC
+#ifndef cmp_timespec
+#define cmp_timespec(TS1, TS2) \
+  ((TS1.ts_sec > TS2.ts_sec || \
+    (TS1.ts_sec == TS2.ts_sec && TS1.ts_nsec > TS2.ts_nsec)) ? 1 : \
+   ((TS1.ts_sec < TS2.ts_sec || \
+     (TS1.ts_sec == TS2.ts_sec && TS1.ts_nsec < TS2.ts_nsec)) ? -1 : 0))
+#endif /* !cmp_timespec */
+#else
+#ifndef cmp_timespec
+#define cmp_timespec(TS1, TS2) \
+  ((TS1.tv_sec > TS2.tv_sec || \
+    (TS1.tv_sec == TS2.tv_sec && TS1.tv_nsec > TS2.tv_nsec)) ? 1 : \
+   ((TS1.tv_sec < TS2.tv_sec || \
+     (TS1.tv_sec == TS2.tv_sec && TS1.tv_nsec < TS2.tv_nsec)) ? -1 : 0))
+#endif /* !cmp_timespec */
+#endif /* HAVE_TIMESPEC_TS_SEC */
+
 	/* safe_mutex adds checking to mutex for easier debugging */
 
 #if defined(__NETWARE__) && !defined(SAFE_MUTEX_DETECT_DESTROY)
diff --git a/include/thr_lock.h b/include/thr_lock.h
index 3dc8857dcd0..527d1288fe4 100644
--- a/include/thr_lock.h
+++ b/include/thr_lock.h
@@ -156,10 +156,12 @@ void thr_lock_data_init(THR_LOCK *lock,THR_LOCK_DATA *data,
 			void *status_param);
 enum enum_thr_lock_result thr_lock(THR_LOCK_DATA *data,
                                    THR_LOCK_OWNER *owner,
-                                   enum thr_lock_type lock_type);
+                                   enum thr_lock_type lock_type,
+                                   ulong lock_wait_timeout);
 void thr_unlock(THR_LOCK_DATA *data);
 enum enum_thr_lock_result thr_multi_lock(THR_LOCK_DATA **data,
-                                         uint count, THR_LOCK_OWNER *owner);
+                                         uint count, THR_LOCK_OWNER *owner,
+                                         ulong lock_wait_timeout);
 void thr_multi_unlock(THR_LOCK_DATA **data,uint count);
 void
 thr_lock_merge_status(THR_LOCK_DATA **data, uint count);
@@ -167,10 +169,12 @@ void thr_abort_locks(THR_LOCK *lock, my_bool upgrade_lock);
 my_bool thr_abort_locks_for_thread(THR_LOCK *lock, my_thread_id thread);
 void thr_print_locks(void);		/* For debugging */
 my_bool thr_upgrade_write_delay_lock(THR_LOCK_DATA *data,
-                                     enum thr_lock_type new_lock_type);
+                                     enum thr_lock_type new_lock_type,
+                                     ulong lock_wait_timeout);
 void    thr_downgrade_write_lock(THR_LOCK_DATA *data,
                                  enum thr_lock_type new_lock_type);
-my_bool thr_reschedule_write_lock(THR_LOCK_DATA *data);
+my_bool thr_reschedule_write_lock(THR_LOCK_DATA *data,
+                                  ulong lock_wait_timeout);
 #ifdef	__cplusplus
 }
 #endif