Bug#30294 blackhole engine causes 100% with 2 alter table statements running (f4c2eff9) · Commits · Software / OSDI20 Artifacts / mariadb

sql/ha_blackhole.cc

+112 −10

Original line number	Diff line number	Diff line
		@@ -22,6 +22,14 @@
		#ifdef HAVE_BLACKHOLE_DB
		#include "ha_blackhole.h"

		/* Static declarations for shared structures */

		static pthread_mutex_t blackhole_mutex;
		static HASH blackhole_open_tables;
		static int blackhole_init= FALSE;

		static st_blackhole_share get_share(const char table_name);
		static void free_share(st_blackhole_share *share);

		/* Blackhole storage engine handlerton */

		@@ -30,7 +38,7 @@ handlerton blackhole_hton= {
		SHOW_OPTION_YES,
		"/dev/null storage engine (anything you write to it disappears)",
		DB_TYPE_BLACKHOLE_DB,
		NULL,
		blackhole_db_init,
		0, /* slot */
		0, /* savepoint size. */
		NULL, /* close_connection */
		@@ -70,15 +78,18 @@ const char **ha_blackhole::bas_ext() const
		int ha_blackhole::open(const char *name, int mode, uint test_if_locked)
		{
		DBUG_ENTER("ha_blackhole::open");
		thr_lock_init(&thr_lock);
		thr_lock_data_init(&thr_lock,&lock,NULL);

		if (!(share= get_share(name)))
		DBUG_RETURN(HA_ERR_OUT_OF_MEM);

		thr_lock_data_init(&share->lock, &lock, NULL);
		DBUG_RETURN(0);
		}

		int ha_blackhole::close(void)
		{
		DBUG_ENTER("ha_blackhole::close");
		thr_lock_delete(&thr_lock);
		free_share(share);
		DBUG_RETURN(0);
		}

		@@ -161,17 +172,23 @@ int ha_blackhole::external_lock(THD *thd, int lock_type)
		}


		uint ha_blackhole::lock_count(void) const
		{
		DBUG_ENTER("ha_blackhole::lock_count");
		DBUG_RETURN(0);
		}

		THR_LOCK_DATA *ha_blackhole::store_lock(THD thd,
		THR_LOCK_DATA **to,
		enum thr_lock_type lock_type)
		{
		DBUG_ENTER("ha_blackhole::store_lock");
		if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)
		{
		if ((lock_type >= TL_WRITE_CONCURRENT_INSERT &&
		lock_type <= TL_WRITE) && !thd->in_lock_tables)
		lock_type = TL_WRITE_ALLOW_WRITE;

		if (lock_type == TL_READ_NO_INSERT && !thd->in_lock_tables)
		lock_type = TL_READ;

		lock.type= lock_type;
		}
		*to++= &lock;
		DBUG_RETURN(to);
		}

		@@ -226,4 +243,89 @@ int ha_blackhole::index_last(byte * buf)
		DBUG_RETURN(HA_ERR_END_OF_FILE);
		}


		static st_blackhole_share get_share(const char table_name)
		{
		st_blackhole_share *share;
		uint length;

		length= (uint) strlen(table_name);
		pthread_mutex_lock(&blackhole_mutex);

		if (!(share= (st_blackhole_share*) hash_search(&blackhole_open_tables,
		(byte*) table_name, length)))
		{
		if (!(share= (st_blackhole_share*) my_malloc(sizeof(st_blackhole_share) +
		length,
		MYF(MY_WME \| MY_ZEROFILL))))
		goto error;

		share->table_name_length= length;
		strmov(share->table_name, table_name);

		if (my_hash_insert(&blackhole_open_tables, (byte*) share))
		{
		my_free((gptr) share, MYF(0));
		share= NULL;
		goto error;
		}

		thr_lock_init(&share->lock);
		}
		share->use_count++;

		error:
		pthread_mutex_unlock(&blackhole_mutex);
		return share;
		}

		static void free_share(st_blackhole_share *share)
		{
		pthread_mutex_lock(&blackhole_mutex);
		if (!--share->use_count)
		hash_delete(&blackhole_open_tables, (byte*) share);
		pthread_mutex_unlock(&blackhole_mutex);
		}


		static byte* blackhole_get_key(st_blackhole_share share, uint length,
		my_bool not_used __attribute__((unused)))
		{
		*length= share->table_name_length;
		return (byte*) share->table_name;
		}


		bool blackhole_db_init()
		{
		DBUG_ENTER("blackhole_db_init");
		if (pthread_mutex_init(&blackhole_mutex, MY_MUTEX_INIT_FAST))
		goto error;
		if (hash_init(&blackhole_open_tables, &my_charset_bin, 32, 0, 0,
		(hash_get_key) blackhole_get_key, 0, 0))
		{
		VOID(pthread_mutex_destroy(&blackhole_mutex));
		}
		else
		{
		blackhole_init= TRUE;
		DBUG_RETURN(FALSE);
		}
		error:
		have_blackhole_db= SHOW_OPTION_DISABLED; // If we couldn't use handler
		DBUG_RETURN(TRUE);
		}


		bool blackhole_db_end()
		{
		if (blackhole_init)
		{
		hash_free(&blackhole_open_tables);
		VOID(pthread_mutex_destroy(&blackhole_mutex));
		}
		blackhole_init= 0;
		return FALSE;
		}

		#endif /* HAVE_BLACKHOLE_DB */

sql/ha_blackhole.h

+16 −2

Original line number	Diff line number	Diff line
		@@ -17,6 +17,18 @@
		#pragma interface /* gcc class implementation */
		#endif


		/*
		Shared structure for correct LOCK operation
		*/
		struct st_blackhole_share {
		THR_LOCK lock;
		uint use_count;
		uint table_name_length;
		char table_name[1];
		};


		/*
		Class definition for the blackhole storage engine
		"Dumbest named feature ever"
		@@ -24,7 +36,7 @@
		class ha_blackhole: public handler
		{
		THR_LOCK_DATA lock; /* MySQL lock */
		THR_LOCK thr_lock;
		st_blackhole_share *share;

		public:
		ha_blackhole(TABLE *table_arg);
		@@ -76,10 +88,12 @@ class ha_blackhole: public handler
		void position(const byte *record);
		int info(uint flag);
		int external_lock(THD *thd, int lock_type);
		uint lock_count(void) const;
		int create(const char name, TABLE table_arg,
		HA_CREATE_INFO *create_info);
		THR_LOCK_DATA *store_lock(THD thd,
		THR_LOCK_DATA **to,
		enum thr_lock_type lock_type);
		};

		bool blackhole_db_init(void);
		bool blackhole_db_end(void);

sql/handler.cc

+4 −0

Original line number	Diff line number	Diff line
		@@ -515,6 +515,10 @@ int ha_panic(enum ha_panic_function flag)
		if (have_berkeley_db == SHOW_OPTION_YES)
		error\|=berkeley_end();
		#endif
		#ifdef HAVE_BLACKHOLE_DB
		if (have_blackhole_db == SHOW_OPTION_YES)
		error\|= blackhole_db_end();
		#endif
		#ifdef HAVE_INNOBASE_DB
		if (have_innodb == SHOW_OPTION_YES)
		error\|=innobase_end();