1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
/*
Copyright (c) 2009, 2010 Sun Microsystems, Inc.
Use is subject to license terms.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
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 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,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */
/**
@file storage/perfschema/pfs_atomic.cc
Atomic operations (implementation).
*/
#include <my_global.h>
#include <my_pthread.h>
#include "pfs_atomic.h"
/*
Using SAFE_MUTEX is impossible, because of recursion.
- code locks mutex X
- P_S records the event
- P_S needs an atomic counter A
- safe mutex called for m_mutex[hash(A)]
- safe mutex allocates/free memory
- safe mutex locks THR_LOCK_malloc
- P_S records the event
- P_S needs an atomic counter B
- safe mutex called for m_mutex[hash(B)]
When hash(A) == hash(B), safe_mutex complains rightly that
the mutex is already locked.
In some cases, A == B, in particular for events_waits_history_long_index.
In short, the implementation of PFS_atomic should not cause events
to be recorded in the performance schema.
Also, because SAFE_MUTEX redefines pthread_mutex_t, etc,
this code is not inlined in pfs_atomic.h, but located here in pfs_atomic.cc.
What is needed is a plain, unmodified, pthread_mutex_t.
This is provided by my_atomic_rwlock_t.
*/
/**
Internal rwlock array.
Using a single rwlock for all atomic operations would be a bottleneck.
Using a rwlock per performance schema structure would be too costly in
memory, and use too many rwlock.
The PFS_atomic implementation computes a hash value from the
atomic variable, to spread the bottleneck across 256 buckets,
while still providing --transparently for the caller-- an atomic
operation.
*/
my_atomic_rwlock_t PFS_atomic::m_rwlock_array[256];
void PFS_atomic::init(void)
{
uint i;
for (i=0; i< array_elements(m_rwlock_array); i++)
my_atomic_rwlock_init(&m_rwlock_array[i]);
}
void PFS_atomic::cleanup(void)
{
uint i;
for (i=0; i< array_elements(m_rwlock_array); i++)
my_atomic_rwlock_destroy(&m_rwlock_array[i]);
}
|
