Re: [PATCH] 2.5.21 Nonlinear CPU support

[Robert Love <rml@tech9.net>]

On Wed, 2002-06-12 at 13:03, H. Peter Anvin wrote:

> while ( 1 ) {
>       disable_preemption();
>       cpu = current_cpu();
>       if ( decompression_buffers[cpu] ) {
> 	 do_decompression(decompression_buffers[cpu]);
> 	 enable_preemption();
> 	 break;		/* DONE, EXIT LOOP */
>       } else {
> 	 enable_preemption();
> 	 down_sem(allocation_semaphore);
> 	 /* Avoid race condition here */
> 	 if ( !decompression_buffers[cpu] )
> 	    decompression_buffers[cpu] = vmalloc(BUFFER_SIZE);
> 	 up_sem(allocation_semaphore);
>       }
> }

Just a note, in 2.5 we recently added put_cpu() and get_cpu() that work
basically like:

	int cpu;

	cpu = get_cpu();
	/* critical non-preemptible section */
	put_cpu();

i.e., a preempt-safe interface to smp_processor_id() that disables and
enables preemption for you... makes it a little easier.

	Robert Love