Bdb 在并发写入时崩溃，c++ linux/osx答案

【问题标题】：Bdb crashes on concurrent write, c++ linux/osxBdb 在并发写入时崩溃，c++ linux/osx
【发布时间】：2011-05-07 04:57:01
【问题描述】：

我在使用 bdb 和锁定机制时遇到问题。

以下代码会导致段错误，或者看起来像死锁/无限循环

#include <iostream>
#include "db_cxx.h"
#include <boost/thread.hpp>

using namespace std;

void thread_instance(Db* db, double start){
double s = start; 
double finish = start + 5000;

for(int x=s; x < finish ; x++){
Dbt key(&x, sizeof(double));
Dbt ddata(&x, sizeof(double));

db->put(NULL, &key, &ddata, 0);
}
}

int
compare_double(DB *dbp, const DBT *a,const DBT *b){
double ai, bi;

memcpy(&ai, a->data, sizeof(double));
memcpy(&bi, b->data, sizeof(double));

return (ai > bi ? 1 : ((ai < bi) ? -1 : 0));
}

int main(){
system("rm data/*");

u_int32_t env_flags = DB_CREATE | DB_INIT_MPOOL | DB_INIT_CDB;

DbEnv* env = new DbEnv(0);
env->set_cachesize(0, 2000000, 1);

u_int32_t m = 0;
env->open("data/", env_flags, 0);

Db* db = new Db(env, 0);
db->set_bt_compare(compare_double);
db->set_flags(DB_DUPSORT);
db->set_pagesize(32768);
db->set_dup_compare(compare_double);

u_int32_t oFlags = DB_CREATE;
try {
db->open(NULL, "db", NULL, DB_BTREE, oFlags, 0);

} catch (DbException &e) {
} catch (std::exception &e) {
}

vector<boost::thread*> threads;

for(int x=0; x < 3; x++){
    threads.push_back(new boost::thread(boost::bind(&thread_instance, db, (x *5000))));
}

for(int x=0; x < threads.size(); x++){
    threads[x]->join();
}
};

我也尝试过 DB_INIT_LOCK，但结果相同。

堆栈轨迹：

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000000000000019
[Switching to process 34816]
0x00000001002e36a7 in __bamc_put ()
(gdb) ba
#0  0x00000001002e36a7 in __bamc_put ()
#1  0x0000000100386689 in __dbc_iput ()
#2  0x0000000100387a6c in __dbc_put ()
#3  0x0000000100383092 in __db_put ()
#4  0x0000000100397888 in __db_put_pp ()
#5  0x00000001002cee59 in Db::put ()
#6  0x0000000100001f88 in thread_instance (db=0x1007006c0, start=5000) at src/main.cpp:16
#7  0x0000000100698254 in thread_proxy ()
#8  0x00007fff80cb9456 in _pthread_start ()
#9  0x00007fff80cb9309 in thread_start ()

有人知道这里会发生什么吗？

【问题讨论】：

标签： berkeley-db

【解决方案1】：

我建议在 db->open 之后检查错误，如果有则打印消息而不是跳过它：捕捉（DbException &e）{ cerr

另外，您似乎没有正确定义标志：至少 DB_THREAD 是必需的，因为您在线程中使用它

【讨论】：