/* g++ -wall -o rwlock rwlock.cpp -lpthread
** 乙個寫優先讀寫鎖的實現，多執行緒頻繁讀，多執行緒少量寫，同時寫優先，效能極佳。
* 當寫鎖(獨佔鎖)lock成功的必要條件是：
* 1. 將寫鎖計數++;
* 2. 會阻塞後續對讀鎖(共享鎖)的讀;
* 3. 等待讀鎖的計數為0;
* 4. 等待寫鎖的計數為1;**/
#include
#include
#include
#include
#include
using
namespace
std;
class
rwlock
void
get_shared_lock
()pthread_mutex_unlock
(&cnt_mutex);}
void
release_shared_lock
()pthread_mutex_unlock
(&cnt_mutex);}
void
get_exclusive_lock
()printf
("*****\t\t w_lock[thread_0x%x] get ok r=%d w=%d\n",(
int)
tag,
rd_cnt
,wr_cnt
);pthread_mutex_unlock
(&cnt_mutex);}
void
release_exclusive_lock()~
rwlock
()};
static
rwlock
lock
;class
test
return
null;}
static
void
*exclusive_task_handler
(void
*)return
null;}
public
:typedef
void*(*
threadfunc)(
void
*);void
start()}
i =100;
ret
=pthread_create
(threads+i
,null
,exclusive_task_handler
,null
);if
(ret !=0
)}};int
main()}
執行結果：
[1257927661
]r_lock
[thread_0xb7c9fba0]r
=1w=
0[1257927661
]r_lock
[thread_0xb749eba0]r
=2w=
0[1257927662
]r_unlock
[thread_0xb7c9fba0]r
=1w=
0[1257927662
]r_unlock
[thread_0xb749eba0]r
=0w=
0r_unlock
[thread_0xb749eba0
]rd_cnt=0
,so singal to wr_cnt[0
]*****[
1257927663
]w_lock
[thread_0xb6c9dba0]r
=0w=
1*****
w_lock
[thread_0xb6c9dba0
]get
ok r=0
w=1[
1257927663
]r_lock
[thread_0xb749eba0]r
=1w=
1r_lock wait
forwr_cnt[1
][1257927663
]r_lock
[thread_0xb7c9fba0]r
=2w=
1r_lock wait
forwr_cnt[1
]*****[
1257927664
]w_unlock
[thread_0xb6c9dba0]r
=2w=
0,then
broadcast
[1257927665
]r_unlock
[thread_0xb749eba0]r
=1w=
0[1257927665
]r_unlock
[thread_0xb7c9fba0]r
=0w=
0r_unlock
[thread_0xb7c9fba0
]rd_cnt=0
,so singal to wr_cnt[0
][1257927666
]r_lock
[thread_0xb749eba0]r
=1w=
0[1257927666
]r_lock
[thread_0xb7c9fba0]r
=2w=
0
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