Re: lockup on Athlon systems, kernel race condition?

[Andrew Morton]

Terence Ripperda wrote:
> 
> ...
>
> asmlinkage long sys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)
> {
>         struct file * filp;
>         unsigned int flag;
>         int on, error = -EBADF;
> 
>         filp = fget(fd);
>         if (!filp)
>                 goto out;
>         error = 0;
>         lock_kernel();    <====
>         switch (cmd) {

This CPU is spinning, waiting for kernel_flag.  It will take the IPI
and the other CPU's smp_call_function() will succeed.

Possibly the IPI has got lost - seems that this is a popular failure mode
for flakey chipsets/motherboards.

Or someone has called sys_ioctl() with interrupts disabled.  That's very
doubtful.