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Date: Wed, 29 Jun 2005 18:59:00 +0200
From: matthieu castet <castet.matthieu@free.fr>
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To: Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: device_remove_file and disconnect
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Hi,

I have a question about sysfs interface.

If you open a sysfs file created by a module, then remove it (rmmoding 
the module that create this sysfs file), then try to read the opened 
file, you often get strange result (segdefault or oppps).

I attach a small program to test it : open your sysfs file with it 
`wait_read /sysfs/file', rmmod the module, and press enter.

I was wondering if it is to user of sysfs to prevent that (with mutex, 
...) or it is a sysfs bug ?

If it is the first case, I fear that lot's of modules are broken.

Regards,

Matthieu

PS : CC me as I am not subscribed to lkml.


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Content-Type: text/x-csrc;
 name="wait_read.c"
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Content-Disposition: inline;
 filename="wait_read.c"

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

int main(int argc, char *argv[])
{
        char c;
        char buf[1024];
        int fd, i, n;

        if (argc != 2)
                return -1;

        fd = open(argv[1], O_RDONLY);
        if (fd < 0) {
                perror("wait_read - open fail");
                return -1;
        }

        c = getc(stdin);
        n = read(fd, buf, 1024);

        for (i = 0; i < n; i++)
                putc(buf[i], stdout);

        if (n < 0)
                perror("wait_read - read fail");
        else
                putc('\n', stdout);

        close(fd);
}

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