私は、セマフォを実装する c のマルチスレッド プロデューサー/コンシューマー プログラムに取り組んでいます。各バッファ構造体には 2 つの一般的なセマフォがあります。1 つは空のバッファ用で、もう 1 つはフル バッファ用です。ただし、プログラムが readInput 関数に入ると、これら 2 つのセマフォの値はランダムな値に変わります。スレッド構造体内のセマフォは問題ありませんが、スレッド構造体内の IO ユニオン内のバッファ構造体内のセマフォが何らかの理由で変更されています。なぜこれが起こっているのですか？
#include "st.h"
#include "semaphore.h"
#include "buffer.h"
/*Definitions here*/
//Input location.
#define DEFAULT_IN stdin
//Output location.
#define DEFAULT_OUT stdout
//Line width
#define LINE_SIZE 80
#define SLEEP_TIME 333333
//Shorthand for structure components
#define INPUT thread->in
#define MUTEX thread->mutex
#define OUTPUT thread->out
/*Global variables here*/
//The input/output can be a stream or a buffer.
typedef union
{
buffer *bufferIO; //Buffer to read from/write to.
FILE *stream; //An I/O stream.
} IO;
//Each thread has an input, a semaphore, and an output.
typedef struct
{
IO in; //Either an input stream or a buffer to read.
semaphore *mutex; //Pointer to a binary semaphore.
IO out; //Either an output stream or a buffer to write.
} Thread;
/*Function prototypes here*/
void *readInput(void *s);
void *processLines(void *s);
void *processAsterisks(void *s);
void *writeOutput(void *s);
int main (int argc, char const *argv[]) //The main function
{
st_init();
/*Binary semaphore*/
semaphore mutex; //Binary semaphore for mutual exclusion.
createSem(&mutex, 1);
printf("Beginning...\n");
/*The three buffers between threads*/
buffer B1, B2, B3;
createBuf(&B1);
createBuf(&B2);
createBuf(&B3);
/*The 5 data locations*/
IO input, buffer1, buffer2, buffer3, output; //stdin, 3 buffers, stdout
/*Set the unions*/
input.stream = DEFAULT_IN; //Input stream
buffer1.bufferIO = &B1; //Contains raw input
buffer2.bufferIO = &B2; //Newlines have become spaces
buffer3.bufferIO = &B3; //** has become ^
output.stream = DEFAULT_OUT; //Output stream, 80 at a time
/*Initialize the threads*/
Thread input_thread = {input, &mutex, buffer1}; //Recieve input
Thread proc1_thread = {buffer1, &mutex, buffer2}; //Returns to spaces
Thread proc2_thread = {buffer2, &mutex, buffer3}; //** to ^
Thread output_thread = {buffer3, &mutex, output}; //Output 80 characters and a newline.
printf("%i\n", input_thread.out.bufferIO->emptyBuffers->value);
/*Create the actual threads*/
if(st_thread_create(readInput, &input_thread, 0, 0) == NULL)
{
perror("st_thread_create for input thread failure");
exit(1);
}
printf("%i\n", input_thread.out.bufferIO->emptyBuffers->value);
if(st_thread_create(processLines, &proc1_thread, 0, 0) == NULL)
{
perror("st_thread_create for line thread failure");
exit(1);
}
if(st_thread_create(processAsterisks, &proc2_thread, 0, 0) == NULL)
{
perror("st_thread_create for asterisk thread failure");
exit(1);
}
if(st_thread_create(writeOutput, &output_thread, 0, 0) == NULL)
{
perror("st_thread_create for output thread failure");
exit(1);
}
st_thread_exit(NULL);
return 0;
}
/*Function definitions here*/
void *readInput(void *s)
{
Thread *thread = s;
char c; //An individual character.
printf("Type some input.\n");
do
{
down(MUTEX);
c = getc(INPUT.stream); //Consume a character from input.
printf("%i\n", OUTPUT.bufferIO->emptyBuffers->value);
deposit(OUTPUT.bufferIO, c); //Produce a character.
up(MUTEX);
st_usleep(SLEEP_TIME); //Wait.
}
while(c != EOF); //Do-while in order to pass on the EOF as an exit flag.
//EOF reached - exit thread.
//assert(c == EOF);
printf("\nDone reading.");
st_thread_exit(NULL);
}...
gdb で調べたところ、次のことがわかりました。
Hardware watchpoint 10: (*(*input_thread.out.bufferIO).emptyBuffers).value
(gdb) c
Continuing.
Hardware watchpoint 10: (*(*input_thread.out.bufferIO).emptyBuffers).value
Old value = 80
New value = 4216725
0x000000395221467c in _dl_runtime_resolve () from /lib64/ld-linux-x86-64.so.2
この _dl_runtime_resolve が何であるかわかりません。