Linux stat 调用超时

Question

有没有办法让 Linux stat 系统调用超时？

我使用的是分布式文件系统，理论上我的所有文件系统调用都应该得到及时响应，但实际上并非如此。经过一段固定的时间后，我宁愿有一个超时和一个错误代码，也不愿继续挂起。

我尝试在另一个线程中生成请求，但这与 gdb 有一些不良交互，并且是表达我真正想要的东西的一种非常迂回的方式：超时。

Answer 1

假设您使用的是 C，并且您可以安全地设置 SIGALARM 处理程序，您可以使用与此类似的代码，只是使用不同的库调用：Can statvfs block on certain network devices? How to handle that case?

几乎剪切和粘贴代码并将statvfs更改为stat：

#include <sigaction.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>

// alarm handler doesn't need to do anything
// other than simply exist
static void alarm_handler( int sig )
{
    return;
}

 .
 .
 .

// stat() with a timeout measured in seconds
// will return -1 with errno set to EINTR should
// it time out
int statvfs_try( const char *path, struct stat *s, unsigned int seconds )
{
    struct sigaction newact;
    struct sigaction oldact;

    // make sure they're entirely clear (yes I'm paranoid...)
    memset( &newact, 0, sizeof( newact ) );
    memset( &oldact, 0, sizeof( oldact) );

    sigemptyset( &newact.sa_mask );

    // note that does not have SA_RESTART set, so
    // stat() should be interrupted on a signal
    // (hopefully your libc doesn't restart it...)
    newact.sa_flags = 0;
    newact.sa_handler = alarm_handler;
    sigaction( SIGALRM, &newact, &oldact );

    alarm( seconds );

    // clear errno
    errno = 0;
    int rc = stat( path, s );

    // save the errno value as alarm() and sigaction() might change it
    int save_errno = errno;

    // clear any alarm and reset the signal handler
    alarm( 0 );
    sigaction( SIGALRM, &oldact, NULL );

    errno = saved_errno;
    return( rc );
}