static int check_lock(struct st_lock_list *list, const char* lock_type,
const char *where, my_bool same_owner, bool no_cond)
{
THR_LOCK_DATA *data,**prev;
uint count=0;
THR_LOCK_OWNER *first_owner;
LINT_INIT(first_owner);
prev= &list->data;
if (list->data)
{
enum thr_lock_type last_lock_type=list->data->type;
if (same_owner && list->data)
first_owner= list->data->owner;
for (data=list->data; data && count++ < MAX_LOCKS ; data=data->next)
{
if (data->type != last_lock_type)
last_lock_type=TL_IGNORE;
if (data->prev != prev)
{
fprintf(stderr,
"Warning: prev link %d didn't point at previous lock at %s: %s\n",
count, lock_type, where);
return 1;
}
if (same_owner &&
!thr_lock_owner_equal(data->owner, first_owner) &&
last_lock_type != TL_WRITE_ALLOW_WRITE)
{
fprintf(stderr,
"Warning: Found locks from different threads in %s: %s\n",
lock_type,where);
return 1;
}
if (no_cond && data->cond)
{
fprintf(stderr,
"Warning: Found active lock with not reset cond %s: %s\n",
lock_type,where);
return 1;
}
prev= &data->next;
}
if (data)
{
fprintf(stderr,"Warning: found too many locks at %s: %s\n",
lock_type,where);
return 1;
}
}
if (prev != list->last)
{
fprintf(stderr,"Warning: last didn't point at last lock at %s: %s\n",
lock_type, where);
return 1;
}
return 0;
}
static inline my_bool
have_old_read_lock(THR_LOCK_DATA *data, THR_LOCK_OWNER *owner)
{
for ( ; data ; data=data->next)
{
if (thr_lock_owner_equal(data->owner, owner))
return 1; /* Already locked by thread */
}
return 0;
}
enum enum_thr_lock_result
thr_lock(THR_LOCK_DATA *data, THR_LOCK_OWNER *owner,
enum thr_lock_type lock_type)
{
THR_LOCK *lock=data->lock;
enum enum_thr_lock_result result= THR_LOCK_SUCCESS;
struct st_lock_list *wait_queue;
THR_LOCK_DATA *lock_owner;
DBUG_ENTER("thr_lock");
data->next=0;
data->cond=0; /* safety */
data->type=lock_type;
data->owner= owner; /* Must be reset ! */
VOID(pthread_mutex_lock(&lock->mutex));
DBUG_PRINT("lock",("data: 0x%lx thread: %ld lock: 0x%lx type: %d",
(long) data, data->owner->info->thread_id,
(long) lock, (int) lock_type));
check_locks(lock,(uint) lock_type <= (uint) TL_READ_NO_INSERT ?
"enter read_lock" : "enter write_lock",0);
if ((int) lock_type <= (int) TL_READ_NO_INSERT)
{
/* Request for READ lock */
if (lock->write.data)
{
/* We can allow a read lock even if there is already a write lock
on the table in one the following cases:
- This thread alread have a write lock on the table
- The write lock is TL_WRITE_ALLOW_READ or TL_WRITE_DELAYED
and the read lock is TL_READ_HIGH_PRIORITY or TL_READ
- The write lock is TL_WRITE_CONCURRENT_INSERT or TL_WRITE_ALLOW_WRITE
and the read lock is not TL_READ_NO_INSERT
*/
DBUG_PRINT("lock",("write locked by thread: %ld",
lock->write.data->owner->info->thread_id));
if (thr_lock_owner_equal(data->owner, lock->write.data->owner) ||
(lock->write.data->type <= TL_WRITE_DELAYED &&
(((int) lock_type <= (int) TL_READ_HIGH_PRIORITY) ||
(lock->write.data->type != TL_WRITE_CONCURRENT_INSERT &&
lock->write.data->type != TL_WRITE_ALLOW_READ))))
{ /* Already got a write lock */
(*lock->read.last)=data; /* Add to running FIFO */
data->prev=lock->read.last;
lock->read.last= &data->next;
if (lock_type == TL_READ_NO_INSERT)
lock->read_no_write_count++;
check_locks(lock,"read lock with old write lock",0);
if (lock->get_status)
(*lock->get_status)(data->status_param, 0);
statistic_increment(locks_immediate,&THR_LOCK_lock);
goto end;
}
if (lock->write.data->type == TL_WRITE_ONLY)
{
/* We are not allowed to get a READ lock in this case */
data->type=TL_UNLOCK;
result= THR_LOCK_ABORTED; /* Can't wait for this one */
goto end;
}
}
else if (!lock->write_wait.data ||
lock->write_wait.data->type <= TL_WRITE_LOW_PRIORITY ||
lock_type == TL_READ_HIGH_PRIORITY ||
have_old_read_lock(lock->read.data, data->owner))
{ /* No important write-locks */
(*lock->read.last)=data; /* Add to running FIFO */
data->prev=lock->read.last;
lock->read.last= &data->next;
if (lock->get_status)
(*lock->get_status)(data->status_param, 0);
if (lock_type == TL_READ_NO_INSERT)
lock->read_no_write_count++;
check_locks(lock,"read lock with no write locks",0);
statistic_increment(locks_immediate,&THR_LOCK_lock);
goto end;
}
/*
We're here if there is an active write lock or no write
lock but a high priority write waiting in the write_wait queue.
In the latter case we should yield the lock to the writer.
*/
wait_queue= &lock->read_wait;
}
else /* Request for WRITE lock */
{
if (lock_type == TL_WRITE_DELAYED)
{
if (lock->write.data && lock->write.data->type == TL_WRITE_ONLY)
{
data->type=TL_UNLOCK;
result= THR_LOCK_ABORTED; /* Can't wait for this one */
goto end;
}
/*
if there is a TL_WRITE_ALLOW_READ lock, we have to wait for a lock
(TL_WRITE_ALLOW_READ is used for ALTER TABLE in MySQL)
*/
if ((!lock->write.data ||
lock->write.data->type != TL_WRITE_ALLOW_READ) &&
!have_specific_lock(lock->write_wait.data,TL_WRITE_ALLOW_READ) &&
(lock->write.data || lock->read.data))
{
/* Add delayed write lock to write_wait queue, and return at once */
(*lock->write_wait.last)=data;
data->prev=lock->write_wait.last;
lock->write_wait.last= &data->next;
data->cond=get_cond();
/*
We don't have to do get_status here as we will do it when we change
the delayed lock to a real write lock
*/
statistic_increment(locks_immediate,&THR_LOCK_lock);
goto end;
}
}
else if (lock_type == TL_WRITE_CONCURRENT_INSERT && ! lock->check_status)
data->type=lock_type= thr_upgraded_concurrent_insert_lock;
if (lock->write.data) /* If there is a write lock */
{
if (lock->write.data->type == TL_WRITE_ONLY)
{
/* We are not allowed to get a lock in this case */
data->type=TL_UNLOCK;
result= THR_LOCK_ABORTED; /* Can't wait for this one */
goto end;
}
/*
The following test will not work if the old lock was a
TL_WRITE_ALLOW_WRITE, TL_WRITE_ALLOW_READ or TL_WRITE_DELAYED in
the same thread, but this will never happen within MySQL.
*/
if (thr_lock_owner_equal(data->owner, lock->write.data->owner) ||
(lock_type == TL_WRITE_ALLOW_WRITE &&
!lock->write_wait.data &&
lock->write.data->type == TL_WRITE_ALLOW_WRITE))
{
/*
We have already got a write lock or all locks are
TL_WRITE_ALLOW_WRITE
*/
DBUG_PRINT("info", ("write_wait.data: 0x%lx old_type: %d",
(ulong) lock->write_wait.data,
lock->write.data->type));
(*lock->write.last)=data; /* Add to running fifo */
data->prev=lock->write.last;
lock->write.last= &data->next;
check_locks(lock,"second write lock",0);
if (data->lock->get_status)
(*data->lock->get_status)(data->status_param, 0);
statistic_increment(locks_immediate,&THR_LOCK_lock);
goto end;
}
DBUG_PRINT("lock",("write locked by thread: %ld",
lock->write.data->owner->info->thread_id));
}
else
{
DBUG_PRINT("info", ("write_wait.data: 0x%lx",
(ulong) lock->write_wait.data));
if (!lock->write_wait.data)
{ /* no scheduled write locks */
my_bool concurrent_insert= 0;
if (lock_type == TL_WRITE_CONCURRENT_INSERT)
{
concurrent_insert= 1;
if ((*lock->check_status)(data->status_param))
{
concurrent_insert= 0;
data->type=lock_type= thr_upgraded_concurrent_insert_lock;
}
}
if (!lock->read.data ||
(lock_type <= TL_WRITE_DELAYED &&
((lock_type != TL_WRITE_CONCURRENT_INSERT &&
lock_type != TL_WRITE_ALLOW_WRITE) ||
!lock->read_no_write_count)))
{
(*lock->write.last)=data; /* Add as current write lock */
data->prev=lock->write.last;
lock->write.last= &data->next;
if (data->lock->get_status)
(*data->lock->get_status)(data->status_param, concurrent_insert);
check_locks(lock,"only write lock",0);
statistic_increment(locks_immediate,&THR_LOCK_lock);
goto end;
}
}
DBUG_PRINT("lock",("write locked by thread: %ld type: %d",
lock->read.data->owner->info->thread_id, data->type));
}
wait_queue= &lock->write_wait;
}
/*
Try to detect a trivial deadlock when using cursors: attempt to
lock a table that is already locked by an open cursor within the
same connection. lock_owner can be zero if we succumbed to a high
priority writer in the write_wait queue.
*/
lock_owner= lock->read.data ? lock->read.data : lock->write.data;
if (lock_owner && lock_owner->owner->info == owner->info)
{
result= THR_LOCK_DEADLOCK;
goto end;
}
/* Can't get lock yet; Wait for it */
DBUG_RETURN(wait_for_lock(wait_queue, data, 0));
end:
pthread_mutex_unlock(&lock->mutex);
DBUG_RETURN(result);
}
static void check_locks(THR_LOCK *lock, const char *where,
my_bool allow_no_locks)
{
uint old_found_errors=found_errors;
DBUG_ENTER("check_locks");
if (found_errors < MAX_FOUND_ERRORS)
{
if (check_lock(&lock->write,"write",where,1,1) |
check_lock(&lock->write_wait,"write_wait",where,0,0) |
check_lock(&lock->read,"read",where,0,1) |
check_lock(&lock->read_wait,"read_wait",where,0,0))
found_errors++;
if (found_errors < MAX_FOUND_ERRORS)
{
uint count=0;
THR_LOCK_DATA *data;
for (data=lock->read.data ; data ; data=data->next)
{
if ((int) data->type == (int) TL_READ_NO_INSERT)
count++;
/* Protect against infinite loop. */
DBUG_ASSERT(count <= lock->read_no_write_count);
}
if (count != lock->read_no_write_count)
{
found_errors++;
fprintf(stderr,
"Warning at '%s': Locks read_no_write_count was %u when it should have been %u\n", where, lock->read_no_write_count,count);
}
if (!lock->write.data)
{
if (!allow_no_locks && !lock->read.data &&
(lock->write_wait.data || lock->read_wait.data))
{
found_errors++;
fprintf(stderr,
"Warning at '%s': No locks in use but locks are in wait queue\n",
where);
}
if (!lock->write_wait.data)
{
if (!allow_no_locks && lock->read_wait.data)
{
found_errors++;
fprintf(stderr,
"Warning at '%s': No write locks and waiting read locks\n",
where);
}
}
else
{
if (!allow_no_locks &&
(((lock->write_wait.data->type == TL_WRITE_CONCURRENT_INSERT ||
lock->write_wait.data->type == TL_WRITE_ALLOW_WRITE) &&
!lock->read_no_write_count) ||
lock->write_wait.data->type == TL_WRITE_ALLOW_READ ||
(lock->write_wait.data->type == TL_WRITE_DELAYED &&
!lock->read.data)))
{
found_errors++;
fprintf(stderr,
"Warning at '%s': Write lock %d waiting while no exclusive read locks\n",where,(int) lock->write_wait.data->type);
}
}
}
else
{ /* Have write lock */
if (lock->write_wait.data)
{
if (!allow_no_locks &&
lock->write.data->type == TL_WRITE_ALLOW_WRITE &&
lock->write_wait.data->type == TL_WRITE_ALLOW_WRITE)
{
found_errors++;
fprintf(stderr,
"Warning at '%s': Found WRITE_ALLOW_WRITE lock waiting for WRITE_ALLOW_WRITE lock\n",
where);
}
}
if (lock->read.data)
{
if (!thr_lock_owner_equal(lock->write.data->owner,
lock->read.data->owner) &&
((lock->write.data->type > TL_WRITE_DELAYED &&
lock->write.data->type != TL_WRITE_ONLY) ||
((lock->write.data->type == TL_WRITE_CONCURRENT_INSERT ||
lock->write.data->type == TL_WRITE_ALLOW_WRITE) &&
lock->read_no_write_count)))
{
found_errors++;
fprintf(stderr,
"Warning at '%s': Found lock of type %d that is write and read locked\n",
where, lock->write.data->type);
DBUG_PRINT("warning",("At '%s': Found lock of type %d that is write and read locked\n",
where, lock->write.data->type));
}
}
if (lock->read_wait.data)
{
if (!allow_no_locks && lock->write.data->type <= TL_WRITE_DELAYED &&
lock->read_wait.data->type <= TL_READ_HIGH_PRIORITY)
{
found_errors++;
fprintf(stderr,
"Warning at '%s': Found read lock of type %d waiting for write lock of type %d\n",
where,
(int) lock->read_wait.data->type,
(int) lock->write.data->type);
}
}
}
}
if (found_errors != old_found_errors)
{
DBUG_PRINT("error",("Found wrong lock"));
}
}
DBUG_VOID_RETURN;
}
enum enum_thr_lock_result
thr_lock(THR_LOCK_DATA *data, THR_LOCK_INFO *owner,
enum thr_lock_type lock_type, ulong lock_wait_timeout,
struct st_my_thread_var *thread_var)
{
THR_LOCK *lock=data->lock;
enum enum_thr_lock_result result= THR_LOCK_SUCCESS;
struct st_lock_list *wait_queue;
MYSQL_TABLE_WAIT_VARIABLES(locker, state) /* no ';' */
DBUG_ENTER("thr_lock");
data->next=0;
data->cond=0; /* safety */
data->type=lock_type;
data->owner= owner; /* Must be reset ! */
MYSQL_START_TABLE_LOCK_WAIT(locker, &state, data->m_psi,
PSI_TABLE_LOCK, lock_type);
mysql_mutex_lock(&lock->mutex);
DBUG_PRINT("lock",("data: 0x%lx thread: 0x%x lock: 0x%lx type: %d",
(long) data, data->owner->thread_id,
(long) lock, (int) lock_type));
check_locks(lock,(uint) lock_type <= (uint) TL_READ_NO_INSERT ?
"enter read_lock" : "enter write_lock",0);
if ((int) lock_type <= (int) TL_READ_NO_INSERT)
{
/* Request for READ lock */
if (lock->write.data)
{
/*
We can allow a read lock even if there is already a
write lock on the table if they are owned by the same
thread or if they satisfy the following lock
compatibility matrix:
Request
/-------
H|++++ WRITE_ALLOW_WRITE
e|+++- WRITE_CONCURRENT_INSERT
l ||||
d ||||
|||\= READ_NO_INSERT
||\ = READ_HIGH_PRIORITY
|\ = READ_WITH_SHARED_LOCKS
\ = READ
+ = Request can be satisified.
- = Request cannot be satisified.
READ_NO_INSERT and WRITE_ALLOW_WRITE should in principle
be incompatible. Before this could have caused starvation of
LOCK TABLE READ in InnoDB under high write load. However
now READ_NO_INSERT is only used for LOCK TABLES READ and this
statement is handled by the MDL subsystem.
See Bug#42147 for more information.
*/
DBUG_PRINT("lock",("write locked 1 by thread: 0x%x",
lock->write.data->owner->thread_id));
if (thr_lock_owner_equal(data->owner, lock->write.data->owner) ||
(lock->write.data->type < TL_WRITE_CONCURRENT_INSERT) ||
((lock->write.data->type == TL_WRITE_CONCURRENT_INSERT) &&
((int) lock_type <= (int) TL_READ_HIGH_PRIORITY)))
{ /* Already got a write lock */
(*lock->read.last)=data; /* Add to running FIFO */
data->prev=lock->read.last;
lock->read.last= &data->next;
if (lock_type == TL_READ_NO_INSERT)
lock->read_no_write_count++;
check_locks(lock,"read lock with old write lock",0);
if (lock->get_status)
(*lock->get_status)(data->status_param, 0);
locks_immediate++;
goto end;
}
if (lock->write.data->type == TL_WRITE_ONLY)
{
/* We are not allowed to get a READ lock in this case */
data->type=TL_UNLOCK;
result= THR_LOCK_ABORTED; /* Can't wait for this one */
goto end;
}
}
else if (!lock->write_wait.data ||
lock->write_wait.data->type <= TL_WRITE_LOW_PRIORITY ||
lock_type == TL_READ_HIGH_PRIORITY ||
has_old_lock(lock->read.data, data->owner)) /* Has old read lock */
{ /* No important write-locks */
(*lock->read.last)=data; /* Add to running FIFO */
data->prev=lock->read.last;
lock->read.last= &data->next;
if (lock->get_status)
(*lock->get_status)(data->status_param, 0);
if (lock_type == TL_READ_NO_INSERT)
lock->read_no_write_count++;
check_locks(lock,"read lock with no write locks",0);
locks_immediate++;
goto end;
}
/*
We're here if there is an active write lock or no write
lock but a high priority write waiting in the write_wait queue.
In the latter case we should yield the lock to the writer.
*/
wait_queue= &lock->read_wait;
}
else /* Request for WRITE lock */
{
if (lock_type == TL_WRITE_CONCURRENT_INSERT && ! lock->check_status)
data->type=lock_type= thr_upgraded_concurrent_insert_lock;
if (lock->write.data) /* If there is a write lock */
{
if (lock->write.data->type == TL_WRITE_ONLY)
{
/* purecov: begin tested */
/* Allow lock owner to bypass TL_WRITE_ONLY. */
if (!thr_lock_owner_equal(data->owner, lock->write.data->owner))
{
/* We are not allowed to get a lock in this case */
data->type=TL_UNLOCK;
result= THR_LOCK_ABORTED; /* Can't wait for this one */
goto end;
}
/* purecov: end */
}
/*
The idea is to allow us to get a lock at once if we already have
a write lock or if there is no pending write locks and if all
write locks are of TL_WRITE_ALLOW_WRITE type.
Note that, since lock requests for the same table are sorted in
such way that requests with higher thr_lock_type value come first
(with one exception (*)), lock being requested usually has
equal or "weaker" type than one which thread might have already
acquired.
*) The only exception to this rule is case when type of old lock
is TL_WRITE_LOW_PRIORITY and type of new lock is changed inside
of thr_lock() from TL_WRITE_CONCURRENT_INSERT to TL_WRITE since
engine turns out to be not supporting concurrent inserts.
Note that since TL_WRITE has the same compatibility rules as
TL_WRITE_LOW_PRIORITY (their only difference is priority),
it is OK to grant new lock without additional checks in such
situation.
Therefore it is OK to allow acquiring write lock on the table if
this thread already holds some write lock on it.
(INSERT INTO t1 VALUES (f1()), where f1() is stored function which
tries to update t1, is an example of statement which requests two
different types of write lock on the same table).
*/
DBUG_ASSERT(! has_old_lock(lock->write.data, data->owner) ||
((lock_type <= lock->write.data->type ||
(lock_type == TL_WRITE &&
lock->write.data->type == TL_WRITE_LOW_PRIORITY))));
if ((lock_type == TL_WRITE_ALLOW_WRITE &&
! lock->write_wait.data &&
lock->write.data->type == TL_WRITE_ALLOW_WRITE) ||
has_old_lock(lock->write.data, data->owner))
{
/*
We have already got a write lock or all locks are
TL_WRITE_ALLOW_WRITE
*/
DBUG_PRINT("info", ("write_wait.data: 0x%lx old_type: %d",
(ulong) lock->write_wait.data,
lock->write.data->type));
(*lock->write.last)=data; /* Add to running fifo */
data->prev=lock->write.last;
lock->write.last= &data->next;
check_locks(lock,"second write lock",0);
if (data->lock->get_status)
(*data->lock->get_status)(data->status_param, 0);
locks_immediate++;
goto end;
}
DBUG_PRINT("lock",("write locked 2 by thread: 0x%x",
lock->write.data->owner->thread_id));
}
else
{
DBUG_PRINT("info", ("write_wait.data: 0x%lx",
(ulong) lock->write_wait.data));
if (!lock->write_wait.data)
{ /* no scheduled write locks */
my_bool concurrent_insert= 0;
if (lock_type == TL_WRITE_CONCURRENT_INSERT)
{
concurrent_insert= 1;
if ((*lock->check_status)(data->status_param))
{
concurrent_insert= 0;
data->type=lock_type= thr_upgraded_concurrent_insert_lock;
}
}
if (!lock->read.data ||
(lock_type <= TL_WRITE_CONCURRENT_INSERT &&
((lock_type != TL_WRITE_CONCURRENT_INSERT &&
lock_type != TL_WRITE_ALLOW_WRITE) ||
!lock->read_no_write_count)))
{
(*lock->write.last)=data; /* Add as current write lock */
data->prev=lock->write.last;
lock->write.last= &data->next;
if (data->lock->get_status)
(*data->lock->get_status)(data->status_param, concurrent_insert);
check_locks(lock,"only write lock",0);
locks_immediate++;
goto end;
}
}
DBUG_PRINT("lock",("write locked 3 by thread: 0x%x type: %d",
lock->read.data->owner->thread_id, data->type));
}
wait_queue= &lock->write_wait;
}
/* Can't get lock yet; Wait for it */
result= wait_for_lock(wait_queue, data, 0, lock_wait_timeout, thread_var);
MYSQL_END_TABLE_LOCK_WAIT(locker);
DBUG_RETURN(result);
end:
mysql_mutex_unlock(&lock->mutex);
MYSQL_END_TABLE_LOCK_WAIT(locker);
DBUG_RETURN(result);
}
