Actually, that doesn't matter, because it's a quickly convergent
operation.
Basically, once you've been invoked on a particular CPU once, you are
pretty much guaranteed to get invoked on that same CPU again, so the
fact that you may end up using a different buffer post-allocation is
not an issue.
Have an array and a semaphore called here allocation_semaphore:
/* PSEUDO-CODE */
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);
}
}
Note that there is no requirement that we're still on cpu "cpu" when
we allocate the buffer. Furthermore, if we fail, we just loop right
back to the top.
-hpa
-- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/