Paul Koning wrote:
I'm really wondering why this is being considered.
A documented property of the form "GCC will use a single instruction
to do X when possible" means exactly nothing. In particular, to call
such a statement a "guarantee" is seriously misleading.
I agree.
If Linux needs the single-instruction property for atomicity, and it
thinks it can rely on this supposed property, then Linux has a bug.
To do atomic operations, you have to use primitives that are
guaranteed always to have the necessary atomicity properties.
Yes.
Typically those would be found in asm statements.
I suspect it would be valuable to have standardized primitives for
atomic actions (semaphores, spinlocks, test-and-set primitives,
circular buffers, pick one).
We already have these in gcc, and they're even documented.
Andrew.
