c++ - 创建了三个线程来实例化同一个类。但是很快只有一个线程继续运行？

Question

创建了三个线程来实例化同一个类。
每个线程都有不同的延迟。但一段时间后只有 1 个线程执行。 ???

GenNum1 = new CGenerateNumbers();
GenNum1->m_threadNumber = 1;
GenNum1->m_usec = 10000;
connect(GenNum1, SIGNAL(OnIndexReady()), this, SLOT(hGenNumOnIndexReady1()));

QThread *tGenNum1 = new QThread;
GenNum1->moveToThread(tGenNum1);
GenNum1->connect(tGenNum1, SIGNAL(started()), GenNum1, SLOT(Started()), Qt::DirectConnection);
tGenNum1->start();




GenNum2 = new CGenerateNumbers();
GenNum2->m_threadNumber = 2;
GenNum2->m_usec = 15000;
connect(GenNum2, SIGNAL(OnIndexReady()), this, SLOT(hGenNumOnIndexReady2()));

QThread *tGenNum2 = new QThread;
GenNum2->moveToThread(tGenNum2);
GenNum2->connect(tGenNum2, SIGNAL(started()), GenNum2, SLOT(Started()), Qt::DirectConnection);
tGenNum2->start();




GenNum3 = new CGenerateNumbers();
GenNum3->m_threadNumber = 3;
GenNum3->m_usec = 20000;
connect(GenNum3, SIGNAL(OnIndexReady()), this, SLOT(hGenNumOnIndexReady3()));

QThread *tGenNum3 = new QThread;
GenNum3->moveToThread(tGenNum3);
GenNum3->connect(tGenNum3, SIGNAL(started()), GenNum3, SLOT(Started()), Qt::DirectConnection);
tGenNum3->start();

---

//this is what each thread calls to:
void CGenerateNumbers::Started()
{
    int i = 0;
    int c = 0;
    char v;

    while(1){
        usleep(m_usec);

        v = (i % 26) + 65;

        for(int j = 0; j < 11; j++){
            mem->m_cmMessageWrite.cMessage[j] = v;
        }
        mem->m_cmMessageWrite.cMessage[0] = m_threadNumber + 48;
        mem->m_cmMessageWrite.cMessage[1] = 32;

        mem->Write();

        m_i = i;

        emit OnIndexReady();
        i++;
    }
}

---

index  index   thread  message

0       0       1 AAAAAAAAA
1       1       2 AAAAAAAAA
2       2       3 AAAAAAAAA
3       3       1 BBBBBBBBB
4       4       1 CCCCCCCCC
5       5       2 BBBBBBBBB
6       6       3 BBBBBBBBB
7       7       1 DDDDDDDDD
8       8       2 CCCCCCCCC
9       9       1 EEEEEEEEE
10      10      3 CCCCCCCCC
11      11      1 FFFFFFFFF
12      12      2 DDDDDDDDD
13      13      1 GGGGGGGGG
14      14      2 EEEEEEEEE
15      15      3 DDDDDDDDD
16      16      1 HHHHHHHHH
17      17      1 IIIIIIIII
18      18      2 FFFFFFFFF
19      19      3 EEEEEEEEE
20      20      1 JJJJJJJJJ
21      21      2 GGGGGGGGG
22      22      1 KKKKKKKKK
23      23      3 FFFFFFFFF
24      24      2 HHHHHHHHH
25      25      1 LLLLLLLLL
26      26      2 IIIIIIIII
27      27      3 GGGGGGGGG
28      28      1 MMMMMMMMM
29      29      1 NNNNNNNNN
30      30      2 JJJJJJJJJ
31      31      3 HHHHHHHHH
32      32      1 OOOOOOOOO
33      33      2 KKKKKKKKK
34      34      1 PPPPPPPPP
35      35      3 IIIIIIIII
36      36      1 QQQQQQQQQ
37      37      2 LLLLLLLLL
38      38      1 RRRRRRRRR
39      39      2 MMMMMMMMM
40      40      1 SSSSSSSSS
41      41      2 NNNNNNNNN
42      42      1 TTTTTTTTT
43      43      1 UUUUUUUUU
44      44      1 VVVVVVVVV
45      45      1 WWWWWWWWW
46      46      2 OOOOOOOOO
47      47      1 XXXXXXXXX
48      48      2 PPPPPPPPP
49      49      1 YYYYYYYYY
50      50      2 QQQQQQQQQ
51      51      1 ZZZZZZZZZ
52      52      1 AAAAAAAAA
53      53      2 RRRRRRRRR
54      54      1 BBBBBBBBB
55      55      2 SSSSSSSSS
56      56      1 CCCCCCCCC
57      57      1 DDDDDDDDD
58      58      2 TTTTTTTTT
59      59      1 EEEEEEEEE
60      60      2 UUUUUUUUU
61      61      1 FFFFFFFFF
62      62      1 GGGGGGGGG
63      63      2 VVVVVVVVV
64      64      1 HHHHHHHHH
65      65      2 WWWWWWWWW
66      66      1 IIIIIIIII
67      67      1 JJJJJJJJJ
68      68      2 XXXXXXXXX
69      69      1 KKKKKKKKK
70      70      2 YYYYYYYYY
71      71      1 LLLLLLLLL
72      72      1 MMMMMMMMM
73      73      2 ZZZZZZZZZ
74      74      1 NNNNNNNNN
75      75      2 AAAAAAAAA
76      76      1 OOOOOOOOO
77      77      1 PPPPPPPPP
78      78      2 BBBBBBBBB
79      79      1 QQQQQQQQQ
80      80      2 CCCCCCCCC
81      81      1 RRRRRRRRR
82      82      1 SSSSSSSSS
83      83      2 DDDDDDDDD
84      84      1 TTTTTTTTT
85      85      2 EEEEEEEEE
86      86      1 UUUUUUUUU
87      87      1 VVVVVVVVV
88      88      2 FFFFFFFFF
89      89      1 WWWWWWWWW
90      90      2 GGGGGGGGG
91      91      1 XXXXXXXXX
92      92      1 YYYYYYYYY
93      93      2 HHHHHHHHH
94      94      1 ZZZZZZZZZ
95      95      2 IIIIIIIII
96      96      1 AAAAAAAAA
97      97      1 BBBBBBBBB
98      98      2 JJJJJJJJJ
99      99      1 CCCCCCCCC
100     100     2 KKKKKKKKK
101     101     1 DDDDDDDDD
102     102     2 LLLLLLLLL
103     103     1 EEEEEEEEE
104     104     2 MMMMMMMMM
105     105     1 FFFFFFFFF
106     106     1 GGGGGGGGG
107     107     2 NNNNNNNNN
108     108     1 HHHHHHHHH
109     109     2 OOOOOOOOO
110     110     1 IIIIIIIII
111     111     1 JJJJJJJJJ
112     112     2 PPPPPPPPP
113     113     1 KKKKKKKKK
114     114     2 QQQQQQQQQ
115     115     1 LLLLLLLLL
116     116     1 MMMMMMMMM
117     117     2 RRRRRRRRR
118     118     1 NNNNNNNNN
119     119     2 SSSSSSSSS
120     120     1 OOOOOOOOO
121     121     1 PPPPPPPPP
122     122     2 TTTTTTTTT
123     123     1 QQQQQQQQQ
124     124     2 UUUUUUUUU
125     125     1 RRRRRRRRR
126     126     2 VVVVVVVVV
127     127     1 SSSSSSSSS
128     128     1 TTTTTTTTT
129     129     2 WWWWWWWWW
130     130     1 UUUUUUUUU
131     131     2 XXXXXXXXX
132     132     1 VVVVVVVVV
133     133     2 YYYYYYYYY
134     134     1 WWWWWWWWW
135     135     1 XXXXXXXXX
136     136     2 ZZZZZZZZZ
137     137     1 YYYYYYYYY
138     138     2 AAAAAAAAA
139     139     1 ZZZZZZZZZ
140     140     1 AAAAAAAAA
141     141     2 BBBBBBBBB
142     142     1 BBBBBBBBB
143     143     2 CCCCCCCCC
144     144     1 CCCCCCCCC
145     145     1 DDDDDDDDD
146     146     2 DDDDDDDDD
147     147     1 EEEEEEEEE
148     148     2 EEEEEEEEE
149     149     1 FFFFFFFFF
150     150     1 GGGGGGGGG
151     151     2 FFFFFFFFF
152     152     1 HHHHHHHHH
153     153     2 GGGGGGGGG
154     154     1 IIIIIIIII
155     155     2 HHHHHHHHH
156     156     1 JJJJJJJJJ
157     157     1 KKKKKKKKK
158     158     2 IIIIIIIII
159     159     1 LLLLLLLLL
160     160     2 JJJJJJJJJ
161     161     1 MMMMMMMMM
162     162     1 NNNNNNNNN
163     163     2 KKKKKKKKK
164     164     1 OOOOOOOOO
165     165     2 LLLLLLLLL
166     166     1 PPPPPPPPP
167     167     1 QQQQQQQQQ
168     168     2 MMMMMMMMM
169     169     1 RRRRRRRRR
170     170     2 NNNNNNNNN
171     171     1 SSSSSSSSS
172     172     1 TTTTTTTTT
173     173     2 OOOOOOOOO
174     174     1 UUUUUUUUU
175     175     2 PPPPPPPPP
176     176     1 VVVVVVVVV
177     177     2 QQQQQQQQQ
178     178     1 WWWWWWWWW
179     179     1 XXXXXXXXX
180     180     2 RRRRRRRRR
181     181     1 YYYYYYYYY
182     182     2 SSSSSSSSS
183     183     1 ZZZZZZZZZ
184     184     1 AAAAAAAAA
185     185     2 TTTTTTTTT
186     186     1 BBBBBBBBB
187     187     2 UUUUUUUUU
188     188     1 CCCCCCCCC
189     189     1 DDDDDDDDD
190     190     2 VVVVVVVVV
191     191     2 WWWWWWWWW
192     192     1 EEEEEEEEE
193     193     1 FFFFFFFFF
194     194     2 XXXXXXXXX
195     195     1 GGGGGGGGG
196     196     2 YYYYYYYYY
197     197     1 HHHHHHHHH
198     198     2 ZZZZZZZZZ
199     199     1 IIIIIIIII
200     200     1 JJJJJJJJJ
201     201     2 AAAAAAAAA
202     202     1 KKKKKKKKK
203     203     2 BBBBBBBBB
204     204     1 LLLLLLLLL
205     205     1 MMMMMMMMM
206     206     2 CCCCCCCCC
207     207     1 NNNNNNNNN
208     208     2 DDDDDDDDD
209     209     1 OOOOOOOOO
210     210     2 EEEEEEEEE
211     211     2 FFFFFFFFF
212     212     1 PPPPPPPPP
213     213     1 QQQQQQQQQ
214     214     1 RRRRRRRRR
215     215     1 SSSSSSSSS
216     216     1 TTTTTTTTT
217     217     1 UUUUUUUUU
218     218     1 VVVVVVVVV
219     219     1 WWWWWWWWW
220     220     1 XXXXXXXXX
221     221     1 YYYYYYYYY
222     222     1 ZZZZZZZZZ
223     223     1 AAAAAAAAA
224     224     1 BBBBBBBBB
225     225     1 CCCCCCCCC
226     226     1 DDDDDDDDD
227     227     1 EEEEEEEEE
228     228     1 FFFFFFFFF
229     229     1 GGGGGGGGG
230     230     1 HHHHHHHHH
231     231     1 IIIIIIIII
232     232     1 JJJJJJJJJ
233     233     1 KKKKKKKKK
234     234     1 LLLLLLLLL
235     235     1 MMMMMMMMM
236     236     1 NNNNNNNNN
237     237     1 OOOOOOOOO
238     238     1 PPPPPPPPP
239     239     1 QQQQQQQQQ
240     240     1 RRRRRRRRR
241     241     1 SSSSSSSSS
242     242     1 TTTTTTTTT
243     243     1 UUUUUUUUU

Answer 1

有两个问题:

1. 您不想告诉 connect 使用直接 连接，只需将其关闭即可，系统会为您正确选择默认值。在这种情况下，您连接的两个 QObject 位于不同的线程中。 QThread 对象存在于当前线程中——它不是线程，而是 Controller 。 CGenerateNumbers 实例存在于新线程中。所以您不想要直接连接，它必须是排队连接!

   在我的应用程序中，我使用的是自定义构建的 Qt，并且我用 QThreadController 完成了 QThread 的全局搜索替换。后者是一个更具描述性和更少误导性的名称。没有真正等同于线程本身的 Qt 类。

2. mem->Write(); 调用可能会阻塞。它不会导致线程“死亡”，而只是阻塞。如果它是一个死锁，就像我认为的那样，线程将永远停止(死锁)。它没有死，只是看起来死了。

下面的代码演示了一个 SSCCE在 Qt 5 和 Qt 4 上都可以正常工作。您需要将代码简化为一个类似的简单示例，我敢打赌您的问题出在未显示的代码上。也许在减少的过程中你会弄清楚。

# threads-18369174.pro
QT       += core
QT       -= gui
TARGET = threads-18369174
CONFIG   += console
CONFIG   -= app_bundle
TEMPLATE = app
SOURCES += main.cpp

.

// main.cpp
#include <QCoreApplication>
#include <QObjectList>
#include <QList>
#include <QThread>
#include <iostream>

const int cycleCount = 500; //!< number of cycles to run at, set to 0 to run forever
const int threadCount = 5; //!< number of threads to create

class Object : public QObject
{
    Q_OBJECT
    int m_threadNumber;
    int m_delayUs;
    volatile bool m_active;
public:
    explicit Object(int delayUs, int no) : m_threadNumber(no), m_delayUs(delayUs) {}
    Q_SIGNAL void indexReady(int);
    Q_SLOT void stop() { m_active = false; }
    Q_SLOT void start()
    {
        m_active = true;
        while (m_active) {
            usleep(m_delayUs);
            emit indexReady(m_threadNumber);
        }
    }
};

class Consumer : public QObject
{
    Q_OBJECT
    QList<Object*> m_objects;
    QList<QThread*> m_threads;
    int m_threadCount; //!< number of active threads in m_threads
    int m_count;
public:
    Consumer() : m_count(0) {}
    void addObject(Object * o) { m_objects << o; }
    void addThread(QThread * t) {
        m_threads << t;
        m_threadCount ++;
        connect(t, SIGNAL(finished()), SLOT(done()));
        connect(t, SIGNAL(terminated()), SLOT(done()));
    }
    Q_SLOT void ready(int n) {
        std::cout << "<" << m_count++ << ":" << n << ">" << std::endl;
        if (m_count == cycleCount) {
            foreach (Object * o, m_objects) o->stop();
            foreach (QThread * t, m_threads) t->wait();
        }
    }
    Q_SLOT void done() {
        QThread * t = qobject_cast<QThread*>(sender());
        int i = m_threads.indexOf(t);
        if (t) t->deleteLater();
        if (i>=0) {
            std::cout << "\nThread " << i << " is done." << std::endl;
            m_threadCount --;
        }
        if (! m_threadCount) qApp->quit();
    }
};

int main(int argc, char *argv[])
{
    Consumer c;
    QObjectList l;
    QCoreApplication a(argc, argv);
    std::cout << "Running under Qt version " << qVersion() << std::endl;
    for (int i = 0; i < threadCount; ++i) {
        Object * o = new Object(10000 + 5000*i, i+1);
        QThread * t = new QThread;
        c.addObject(o);
        c.addThread(t);
        o->moveToThread(t);
        o->connect(t, SIGNAL(started()), SLOT(start()));
        c.connect(o, SIGNAL(indexReady(int)), SLOT(ready(int)));
        t->start();
        t->exit();
        l << o;
    }
    return a.exec();
}

#include "main.moc"