Possible race in interruptible_sleep_on_timeout()

From: Richard B. Johnson (root@chaos.analogic.com)
Date: Wed May 16 2001 - 10:55:12 EST

I lifted the following kernel-thread code from
../linux/drivers/net/8139too.c, just added a procedure to call.

static int gpib_thread(void *unused)
{
    unsigned long timeout;

    daemonize();
    spin_lock_irq(&current->sigmask_lock);
    sigemptyset(&current->blocked);
    recalc_sigpending(current);
    spin_unlock_irq(&current->sigmask_lock);
    memcpy(current->comm, task_name, sizeof(task_name));
    for(;;)
    {
        timeout = 0x02;
        do {
           timeout = interruptible_sleep_on_timeout(&info->twait, timeout);
           } while (!signal_pending(current)&&(timeout > 0));
        if(signal_pending(current))
            up_and_exit(&info->quit, 0);
        tinker(info->what_to_do);
    }
}

It has been observed that, given the conditions of little or no
CPU activity except `top`, procedure "tinker()" will never get
executed because interruptible_sleep_on_timeout returns the
same timeout value it received.

This is on kernel version 2.4.1. Maybe this race has been found and
fixed?

Cheers,
Dick Johnson

Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).

"Memory is like gasoline. You use it up when you are running. Of
course you get it all back when you reboot..."; Actual explanation
obtained from the Micro$oft help desk.

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This archive was generated by hypermail 2b29 : Wed May 23 2001 - 21:00:17 EST