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我目前的进展如下，

通过以下方式启用 Bootchart.h

#ifndef BOOTCHART
# define  BOOTCHART  1
#endif

之后我编译代码，使 INIT_BOOTCHART=true kernel -j4。所以编译完成后我做了

1. adb root
2. adb shell
3. cd data
4. echo 120 > bootchart-start (cat bootchart-start -> 120)
5. mkdir bootchart
6. reboot bootloader
7. fastboot flash kernel kernel.img
8. reboot

然后我检查 data/bootchart 文件夹内的日志文件。但几分钟后它也是空的。

所以我把一些日志放在 system/core/init/init.c -> bootchart_init_action

static int bootchart_init_action(int nargs, char **args)
{

    ERROR("#### JACH #### - BOOTCHART'%d':'%s'\n", 0, "bootchart_init_action -start");

    bootchart_count = bootchart_init();
        ERROR("#### JACH #### - BOOTCHART'%d':'%s'\n", bootchart_count, "bootchart_init_action -bootchart_count");
    if (bootchart_count < 0) {
        ERROR("bootcharting init failure\n");
    } else if (bootchart_count > 0) {
        NOTICE("bootcharting started (period=%d ms)\n", bootchart_count*BOOTCHART_POLLING_MS);
    } else {
        NOTICE("bootcharting ignored\n");
    }

    ERROR("#### JACH #### - BOOTCHART'%d':'%s'\n", 0, "bootchart_init_action -end");

    return 0;
}

编译上述代码后，我看到 bootchart_init() 函数返回 0 值。下面是日志文件。

<11>[    2.814551] init: #### JACH #### - BOOTCHART'0':'bootchart_init_action -start'
<11>[    2.814591] init: #### JACH #### - bootchart_init'0':'start'
<11>[    2.814704] init: #### JACH #### - BOOTCHART'0':'bootchart_init_action -bootchart_count'
<11>[    2.814721] init: #### JACH #### - BOOTCHART'0':'bootchart_init_action -end'

所以 bootchart_init() 如下：

#define LOG_STARTFILE   "/data/bootchart-start"

int   bootchart_init( void )
{
    ERROR("#### JACH #### - bootchart_init'%d':'%s'\n", 0, "start");
    int  ret;
    char buff[4];
    int  timeout = 0, count = 0;

    buff[0] = 0;
    proc_read( LOG_STARTFILE, buff, sizeof(buff) );
    if (buff[0] != 0) {
        timeout = atoi(buff);;
    ERROR("#### JACH #### - bootchart_init'%d':'%s'\n", timeout, "timeout");

    }
    else {
        /* when running with emulator, androidboot.bootchart=<timeout>
         * might be passed by as kernel parameters to specify the bootchart
         * timeout. this is useful when using -wipe-data since the /data
         * partition is fresh
         */
        char  cmdline[1024];
        char* s;
#define  KERNEL_OPTION  "androidboot.bootchart="
        proc_read( "/proc/cmdline", cmdline, sizeof(cmdline) );
        s = strstr(cmdline, KERNEL_OPTION);
        if (s) {
            s      += sizeof(KERNEL_OPTION)-1;
            timeout = atoi(s);
        }
    }
    if (timeout == 0)
        return 0;

    if (timeout > BOOTCHART_MAX_TIME_SEC)
        timeout = BOOTCHART_MAX_TIME_SEC;

    count = (timeout*1000 + BOOTCHART_POLLING_MS-1)/BOOTCHART_POLLING_MS;

    do {ret=mkdir(LOG_ROOT,0755);}while (ret < 0 && errno == EINTR);

    file_buff_open(log_stat,  LOG_STAT);
    file_buff_open(log_procs, LOG_PROCS);
    file_buff_open(log_disks, LOG_DISK);

    /* create kernel process accounting file */
    {
        int  fd = open( LOG_ACCT, O_WRONLY|O_CREAT|O_TRUNC,0644);
        if (fd >= 0) {
            close(fd);
            acct( LOG_ACCT );
        }
    }

    log_header();
    ERROR("#### JACH #### - bootchart_init'%d':'%s'\n", 0, "end");
    return count;
}

我猜在启动时上面的代码（proc_read( LOG_STARTFILE, buff, sizeof(buff) );）没有读取或写入数据的权限，或者没有创建文件分区。而且我对超时进行了硬编码，但bootchart_step()功能仍然有效，但是日志文件没有写入 data/bootchart 文件夹。

但我不知道如何启用这个问题。感谢您参加我的提问。

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