修复签章浮动靠左问题
This commit is contained in:
lihansani
221
mysql/include/thr_rwlock.h
Normal file
221
mysql/include/thr_rwlock.h
Normal file
@@ -0,0 +1,221 @@
|
||||
#ifndef THR_RWLOCK_INCLUDED
|
||||
#define THR_RWLOCK_INCLUDED
|
||||
|
||||
/* Copyright (c) 2014, 2023, Oracle and/or its affiliates.
|
||||
|
||||
This program is free software; you can redistribute it and/or modify
|
||||
it under the terms of the GNU General Public License, version 2.0,
|
||||
as published by the Free Software Foundation.
|
||||
|
||||
This program is also distributed with certain software (including
|
||||
but not limited to OpenSSL) that is licensed under separate terms,
|
||||
as designated in a particular file or component or in included license
|
||||
documentation. The authors of MySQL hereby grant you an additional
|
||||
permission to link the program and your derivative works with the
|
||||
separately licensed software that they have included with MySQL.
|
||||
|
||||
This program is distributed in the hope that it will be useful,
|
||||
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
GNU General Public License, version 2.0, for more details.
|
||||
|
||||
You should have received a copy of the GNU General Public License
|
||||
along with this program; if not, write to the Free Software
|
||||
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
|
||||
|
||||
/**
|
||||
MySQL rwlock implementation.
|
||||
|
||||
There are two "layers":
|
||||
1) native_rw_*()
|
||||
Functions that map directly down to OS primitives.
|
||||
Windows - SRWLock
|
||||
Other OSes - pthread
|
||||
2) mysql_rw*()
|
||||
Functions that include Performance Schema instrumentation.
|
||||
See include/mysql/psi/mysql_thread.h
|
||||
|
||||
This file also includes rw_pr_*(), which implements a special
|
||||
version of rwlocks that prefer readers. The P_S version of these
|
||||
are mysql_prlock_*() - see include/mysql/psi/mysql_thread.h
|
||||
*/
|
||||
|
||||
#include "my_global.h"
|
||||
#include "my_thread.h"
|
||||
#include "thr_cond.h"
|
||||
|
||||
C_MODE_START
|
||||
|
||||
#ifdef _WIN32
|
||||
typedef struct st_my_rw_lock_t
|
||||
{
|
||||
SRWLOCK srwlock; /* native reader writer lock */
|
||||
BOOL have_exclusive_srwlock; /* used for unlock */
|
||||
} native_rw_lock_t;
|
||||
#else
|
||||
typedef pthread_rwlock_t native_rw_lock_t;
|
||||
#endif
|
||||
|
||||
static inline int native_rw_init(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
InitializeSRWLock(&rwp->srwlock);
|
||||
rwp->have_exclusive_srwlock = FALSE;
|
||||
return 0;
|
||||
#else
|
||||
/* pthread_rwlockattr_t is not used in MySQL */
|
||||
return pthread_rwlock_init(rwp, NULL);
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline int native_rw_destroy(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
return 0; /* no destroy function */
|
||||
#else
|
||||
return pthread_rwlock_destroy(rwp);
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline int native_rw_rdlock(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
AcquireSRWLockShared(&rwp->srwlock);
|
||||
return 0;
|
||||
#else
|
||||
return pthread_rwlock_rdlock(rwp);
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline int native_rw_tryrdlock(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
if (!TryAcquireSRWLockShared(&rwp->srwlock))
|
||||
return EBUSY;
|
||||
return 0;
|
||||
#else
|
||||
return pthread_rwlock_tryrdlock(rwp);
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline int native_rw_wrlock(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
AcquireSRWLockExclusive(&rwp->srwlock);
|
||||
rwp->have_exclusive_srwlock= TRUE;
|
||||
return 0;
|
||||
#else
|
||||
return pthread_rwlock_wrlock(rwp);
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline int native_rw_trywrlock(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
if (!TryAcquireSRWLockExclusive(&rwp->srwlock))
|
||||
return EBUSY;
|
||||
rwp->have_exclusive_srwlock= TRUE;
|
||||
return 0;
|
||||
#else
|
||||
return pthread_rwlock_trywrlock(rwp);
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline int native_rw_unlock(native_rw_lock_t *rwp)
|
||||
{
|
||||
#ifdef _WIN32
|
||||
if (rwp->have_exclusive_srwlock)
|
||||
{
|
||||
rwp->have_exclusive_srwlock= FALSE;
|
||||
ReleaseSRWLockExclusive(&rwp->srwlock);
|
||||
}
|
||||
else
|
||||
ReleaseSRWLockShared(&rwp->srwlock);
|
||||
return 0;
|
||||
#else
|
||||
return pthread_rwlock_unlock(rwp);
|
||||
#endif
|
||||
}
|
||||
|
||||
|
||||
/**
|
||||
Portable implementation of special type of read-write locks.
|
||||
|
||||
These locks have two properties which are unusual for rwlocks:
|
||||
1) They "prefer readers" in the sense that they do not allow
|
||||
situations in which rwlock is rd-locked and there is a
|
||||
pending rd-lock which is blocked (e.g. due to pending
|
||||
request for wr-lock).
|
||||
This is a stronger guarantee than one which is provided for
|
||||
PTHREAD_RWLOCK_PREFER_READER_NP rwlocks in Linux.
|
||||
MDL subsystem deadlock detector relies on this property for
|
||||
its correctness.
|
||||
2) They are optimized for uncontended wr-lock/unlock case.
|
||||
This is scenario in which they are most oftenly used
|
||||
within MDL subsystem. Optimizing for it gives significant
|
||||
performance improvements in some of tests involving many
|
||||
connections.
|
||||
|
||||
Another important requirement imposed on this type of rwlock
|
||||
by the MDL subsystem is that it should be OK to destroy rwlock
|
||||
object which is in unlocked state even though some threads might
|
||||
have not yet fully left unlock operation for it (of course there
|
||||
is an external guarantee that no thread will try to lock rwlock
|
||||
which is destroyed).
|
||||
Putting it another way the unlock operation should not access
|
||||
rwlock data after changing its state to unlocked.
|
||||
|
||||
TODO/FIXME: We should consider alleviating this requirement as
|
||||
it blocks us from doing certain performance optimizations.
|
||||
*/
|
||||
|
||||
typedef struct st_rw_pr_lock_t {
|
||||
/**
|
||||
Lock which protects the structure.
|
||||
Also held for the duration of wr-lock.
|
||||
*/
|
||||
native_mutex_t lock;
|
||||
/**
|
||||
Condition variable which is used to wake-up
|
||||
writers waiting for readers to go away.
|
||||
*/
|
||||
native_cond_t no_active_readers;
|
||||
/** Number of active readers. */
|
||||
uint active_readers;
|
||||
/** Number of writers waiting for readers to go away. */
|
||||
uint writers_waiting_readers;
|
||||
/** Indicates whether there is an active writer. */
|
||||
my_bool active_writer;
|
||||
#ifdef SAFE_MUTEX
|
||||
/** Thread holding wr-lock (for debug purposes only). */
|
||||
my_thread_t writer_thread;
|
||||
#endif
|
||||
} rw_pr_lock_t;
|
||||
|
||||
extern int rw_pr_init(rw_pr_lock_t *);
|
||||
extern int rw_pr_rdlock(rw_pr_lock_t *);
|
||||
extern int rw_pr_wrlock(rw_pr_lock_t *);
|
||||
extern int rw_pr_unlock(rw_pr_lock_t *);
|
||||
extern int rw_pr_destroy(rw_pr_lock_t *);
|
||||
|
||||
static inline void
|
||||
rw_pr_lock_assert_write_owner(const rw_pr_lock_t *rwlock MY_ATTRIBUTE((unused)))
|
||||
{
|
||||
#ifdef SAFE_MUTEX
|
||||
assert(rwlock->active_writer &&
|
||||
my_thread_equal(my_thread_self(), rwlock->writer_thread));
|
||||
#endif
|
||||
}
|
||||
|
||||
static inline void
|
||||
rw_pr_lock_assert_not_write_owner(const rw_pr_lock_t *rwlock MY_ATTRIBUTE((unused)))
|
||||
{
|
||||
#ifdef SAFE_MUTEX
|
||||
assert(!rwlock->active_writer ||
|
||||
!my_thread_equal(my_thread_self(), rwlock->writer_thread));
|
||||
#endif
|
||||
}
|
||||
|
||||
C_MODE_END
|
||||
|
||||
#endif /* THR_RWLOCK_INCLUDED */
|
||||
Reference in New Issue
Block a user