linux操作系统银行家代码

银行家算法是一种用于避免死锁的算法，它用来确保在分配资源时不会进入不安全的状态。以下是一个在Linux操作系统下实现银行家算法的示例代码：

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>

#define MAX_PROCESSES 10
#define MAX_RESOURCES 10

int available[MAX_RESOURCES];
int allocation[MAX_PROCESSES][MAX_RESOURCES];
int max[MAX_PROCESSES][MAX_RESOURCES];
int need[MAX_PROCESSES][MAX_RESOURCES];
bool finished[MAX_PROCESSES] = {false};

int num_processes;
int num_resources;

bool is_safe() {
    int work[MAX_RESOURCES];
    for (int i = 0; i < num_resources; i++) {
        work[i] = available[i];
    }

    bool can_finish = true;
    int safe_sequence[MAX_PROCESSES];
    int num_finished = 0;

    while (num_finished < num_processes && can_finish) {
        can_finish = false;

        for (int i = 0; i < num_processes; i++) {
            if (!finished[i]) {
                bool can_allocate = true;

                for (int j = 0; j < num_resources; j++) {
                    if (need[i][j] > work[j]) {
                        can_allocate = false;
                        break;
                    }
                }

                if (can_allocate) {
                    for (int j = 0; j < num_resources; j++) {
                        work[j] += allocation[i][j];
                    }

                    safe_sequence[num_finished] = i;
                    num_finished++;
                    finished[i] = true;
                    can_finish = true;
                }
            }
        }
    }

    if (num_finished == num_processes) {
        printf("Safe sequence: ");
        for (int i = 0; i < num_processes; i++) {
            printf("%d ", safe_sequence[i]);
        }
        printf("\n");

        return true;
    } else {
        printf("Not safe!\n");

        return false;
    }
}

int request_resources(int pid, int *request) {
    for (int i = 0; i < num_resources; i++) {
        if (request[i] > need[pid][i] || request[i] > available[i]) {
            return -1;
        }
    }

    for (int i = 0; i < num_resources; i++) {
        available[i] -= request[i];
        allocation[pid][i] += request[i];
        need[pid][i] -= request[i];
    }

    if (is_safe()) {
        return 0;
    } else {
        for (int i = 0; i < num_resources; i++) {
            available[i] += request[i];
            allocation[pid][i] -= request[i];
            need[pid][i] += request[i];
        }

        return -1;
    }
}

int release_resources(int pid, int *release) {
    for (int i = 0; i < num_resources; i++) {
        if (release[i] > allocation[pid][i]) {
            return -1;
        }
    }

    for (int i = 0; i < num_resources; i++) {
        available[i] += release[i];
        allocation[pid][i] -= release[i];
        need[pid][i] += release[i];
    }

    return 0;
}

int main(int argc, char **argv) {
    if (argc <= 1) {
        printf("Usage: ./banker <num_processes> <num_resources> <resource1> ... <resourceN>\n");
        return -1;
    }

    num_processes = atoi(argv[1]);
    num_resources = atoi(argv[2]);

    if (num_processes > MAX_PROCESSES || num_resources > MAX_RESOURCES) {
        printf("Too many processes or resources!\n");
        return -1;
    }

    for (int i = 0; i < num_resources; i++) {
        available[i] = atoi(argv[3 + i]);
    }

    for (int i = 0; i < num_processes; i++) {
        for (int j = 0; j < num_resources; j++) {
            allocation[i][j] = 0;
            need[i][j] = 0;
            finished[i] = false;
        }
    }

    while (true) {
        char command;
        int pid;
        int request[MAX_RESOURCES];
        int release[MAX_RESOURCES];

        printf("> ");
        if (scanf("%c", &command) == EOF) {
            break;
        }

        switch (command) {
            case 'i':
                scanf("%d", &pid);
                for (int i = 0; i < num_resources; i++) {
                    scanf("%d", &max[pid][i]);
                    need[pid][i] = max[pid][i] - allocation[pid][i];
                }
                break;

            case 'q':
                scanf("%d", &pid);
                for (int i = 0; i < num_resources; i++) {
                    printf("%d ", need[pid][i]);
                }
                printf("\n");
                break;

            case 'r':
                scanf("%d", &pid);
                for (int i = 0; i < num_resources; i++) {
                    scanf("%d", &request[i]);
                }
                if (request_resources(pid, request) == -1) {
                    printf("Request denied\n");
                }
                break;

            case 'f':
                scanf("%d", &pid);
                for (int i = 0; i < num_resources; i++) {
                    scanf("%d", &release[i]);
                }
                release_resources(pid, release);
                break;

            case 's':
                is_safe();
                break;

            default:
                break;
        }

        while (getchar() != '\n');
    }

    return 0;
}

该代码使用命令行界面与用户进行交互，支持以下命令：

- `i <pid> <r1> <r2> ... <rn>`：为进程 `<pid>` 指定最大的资源需求量。
- `q <pid>`：查询进程 `<pid>` 的当前资源需求量。
- `r <pid> <r1> <r2> ... <rn>`：请求进程 `<pid>` 的资源。
- `f <pid> <r1> <r2> ... <rn>`：释放进程 `<pid>` 的资源。
- `s`：检查系统是否处于安全状态。

可以根据需要进行修改和扩展。