Commit ae17c3c7 authored by unknown's avatar unknown
Browse files

ha_innodb.cc, trx0trx.h, lock0lock.c, trx0trx.c: 

Reserve the MySQL LOCK_thread_count mutex when printing thd->query of
an arbitrary transaction; if we are printing thd->query of a transaction that
we know is currently executing inside InnoDB, then we know that MySQL cannot
meanwhile change thd->query, and no need to reserve the MySQL mutex; note
that this patch still leaves open the possibility of races in MySQL's
thd->query_len


innobase/trx/trx0trx.c:
  Reserve the MySQL LOCK_thread_count mutex when printing thd->query of an arbitrary transaction; if we are printing thd->query of the a transaction that we know is currently executing inside InnoDB, then we know that MySQL cannot meanwhile change thd->query, and no need to reserve the MySQL mutex; note that thsi patch still leaves aopen the possibility of races in MySQL's thd->query_len
innobase/lock/lock0lock.c:
  Reserve the MySQL LOCK_thread_count mutex when printing thd->query of an arbitrary transaction; if we are printing thd->query of the a transaction that we know is currently executing inside InnoDB, then we know that MySQL cannot meanwhile change thd->query, and no need to reserve the MySQL mutex; note that thsi patch still leaves aopen the possibility of races in MySQL's thd->query_len
innobase/include/trx0trx.h:
  Reserve the MySQL LOCK_thread_count mutex when printing thd->query of an arbitrary transaction; if we are printing thd->query of the a transaction that we know is currently executing inside InnoDB, then we know that MySQL cannot meanwhile change thd->query, and no need to reserve the MySQL mutex; note that thsi patch still leaves aopen the possibility of races in MySQL's thd->query_len
sql/ha_innodb.cc:
  Reserve the MySQL LOCK_thread_count mutex when printing thd->query of an arbitrary transaction; if we are printing thd->query of the a transaction that we know is currently executing inside InnoDB, then we know that MySQL cannot meanwhile change thd->query, and no need to reserve the MySQL mutex; note that thsi patch still leaves aopen the possibility of races in MySQL's thd->query_len
parent e5a2fc8e

innobase/include/trx0trx.h

+4 −2
Original line number Diff line number Diff line
@@ -275,7 +275,9 @@ trx_commit_step( 
	que_thr_t*	thr);	/* in: query thread */

/**************************************************************************

Prints info about a transaction to the standard output. The caller must

own the kernel mutex. */

own the kernel mutex and must have called

innobase_mysql_prepare_print_arbitrary_thd(), unless he knows that MySQL or

InnoDB cannot meanwhile change the info printed here. */



void

trx_print(

innobase/lock/lock0lock.c

+34 −0
Original line number Diff line number Diff line
@@ -17,6 +17,32 @@ Created 5/7/1996 Heikki Tuuri 
#include "dict0mem.h"

#include "trx0sys.h"





/* 2 function prototypes copied from ha_innodb.cc: */



/*****************************************************************

If you want to print a thd that is not associated with the current thread,

you must call this function before reserving the InnoDB kernel_mutex, to

protect MySQL from setting thd->query NULL. If you print a thd of the current

thread, we know that MySQL cannot modify thd->query, and it is not necessary

to call this. Call innobase_mysql_end_print_arbitrary_thd() after you release

the kernel_mutex.

NOTE that /mysql/innobase/lock/lock0lock.c must contain the prototype for this

function! */



void

innobase_mysql_prepare_print_arbitrary_thd(void);

/*============================================*/



/*****************************************************************

Relases the mutex reserved by innobase_mysql_prepare_print_arbitrary_thd().

NOTE that /mysql/innobase/lock/lock0lock.c must contain the prototype for this

function! */



void

innobase_mysql_end_print_arbitrary_thd(void);

/*========================================*/



/* Restricts the length of search we will do in the waits-for

graph of transactions */

#define LOCK_MAX_N_STEPS_IN_DEADLOCK_CHECK 1000000
@@ -3974,6 +4000,11 @@ lock_print_info( 
	ulint	i;

	mtr_t	mtr;



	/* We must protect the MySQL thd->query field with a MySQL mutex, and

	because the MySQL mutex must be reserved before the kernel_mutex of

	InnoDB, we call innobase_mysql_prepare_print_arbitrary_thd() here. */



	innobase_mysql_prepare_print_arbitrary_thd();

	lock_mutex_enter_kernel();



	if (lock_deadlock_found) {
@@ -4037,6 +4068,7 @@ lock_print_info( 


	if (trx == NULL) {

		lock_mutex_exit_kernel();

		innobase_mysql_end_print_arbitrary_thd();



		ut_ad(lock_validate());
@@ -4101,6 +4133,7 @@ lock_print_info( 


 		if (load_page_first) {

			lock_mutex_exit_kernel();

			innobase_mysql_end_print_arbitrary_thd();



			mtr_start(&mtr);
@@ -4110,6 +4143,7 @@ lock_print_info( 


			load_page_first = FALSE;



			innobase_mysql_prepare_print_arbitrary_thd();

			lock_mutex_enter_kernel();



			goto loop;

innobase/trx/trx0trx.c

+3 −1
Original line number Diff line number Diff line
@@ -1562,7 +1562,9 @@ trx_mark_sql_stat_end( 


/**************************************************************************

Prints info about a transaction to the standard output. The caller must

own the kernel mutex. */

own the kernel mutex and must have called

innobase_mysql_prepare_print_arbitrary_thd(), unless he knows that MySQL or

InnoDB cannot meanwhile change the info printed here. */



void

trx_print(

sql/ha_innodb.cc

+34 −14
Original line number Diff line number Diff line
@@ -312,6 +312,35 @@ convert_error_code_to_mysql( 
    	}

}



/*****************************************************************

If you want to print a thd that is not associated with the current thread,

you must call this function before reserving the InnoDB kernel_mutex, to

protect MySQL from setting thd->query NULL. If you print a thd of the current

thread, we know that MySQL cannot modify thd->query, and it is not necessary

to call this. Call innobase_mysql_end_print_arbitrary_thd() after you release

the kernel_mutex.

NOTE that /mysql/innobase/lock/lock0lock.c must contain the prototype for this

function! */

extern "C"

void

innobase_mysql_prepare_print_arbitrary_thd(void)

/*============================================*/

{

	VOID(pthread_mutex_lock(&LOCK_thread_count));

}



/*****************************************************************

Relases the mutex reserved by innobase_mysql_prepare_print_arbitrary_thd().

NOTE that /mysql/innobase/lock/lock0lock.c must contain the prototype for this

function! */

extern "C"

void

innobase_mysql_end_print_arbitrary_thd(void)

/*========================================*/

{

	VOID(pthread_mutex_unlock(&LOCK_thread_count));

}



/*****************************************************************

Prints info of a THD object (== user session thread) to the

standard output. NOTE that /mysql/innobase/trx/trx0trx.c must contain
@@ -329,15 +358,6 @@ innobase_mysql_print_thd( 


        thd = (const THD*) input_thd;



/* We cannot use LOCK_thread_count to protect this operation because we own

the InnoDB kernel_mutex when we enter this function, but in freeing of a

THD object, MySQL first reserves LOCK_thread_count and AFTER THAT InnoDB

reserves kernel_mutex when freeing the trx object => a deadlock can occur.

The solution is for MySQL to use a separate mutex to protect thd->query and

thd->query_len. Someone should do that! This bug has been here for 3 years!



	VOID(pthread_mutex_lock(&LOCK_thread_count)); */



  	fprintf(f, "MySQL thread id %lu, query id %lu",

		thd->thread_id, thd->query_id);

	if (thd->host) {
@@ -367,14 +387,16 @@ thd->query_len. Someone should do that! This bug has been here for 3 years! 
		len = thd->query_length;



		if (len > 300) {

			len = 300;	/* A TEMPORARY SOLUTION: print at most

			len = 300;	/* ADDITIONAL SAFETY: print at most

					300 chars to reduce the probability of

					a seg fault in a race */

					a seg fault if there is a race in

					thd->query_len in MySQL; on May 13,

					2004 we do not know */

		}

		

		for (i = 0; i < len && s[i]; i++);



		memcpy(buf, s, i);	/* use memcpy to reduce the timeframe

		memcpy(buf, s, i);	/* Use memcpy to reduce the timeframe

					for a race, compared to fwrite() */

		buf[300] = '\0';
@@ -383,8 +405,6 @@ thd->query_len. Someone should do that! This bug has been here for 3 years! 
	}



	putc('\n', f);



/*	VOID(pthread_mutex_unlock(&LOCK_thread_count)); */

}



/*************************************************************************