On Mon, Oct 18, 2010 at 02:46:55PM +0200, Peter Zijlstra wrote: > On Mon, 2010-10-18 at 09:44 +0200, Ohad Ben-Cohen wrote: > > OMAP4 introduces a Spinlock hardware module, which provides hardware > > assistance for synchronization and mutual exclusion between heterogeneous > > processors and those not operating under a single, shared operating system > > (e.g. OMAP4 has dual Cortex-A9, dual Cortex-M3 and a C64x+ DSP). > > I just have to ask... was it really easier to build silicon than to > agree on a spinlock ABI? I'm not really sure what point you're trying to make, but if you're suggesting that Linux's spinlock should be exposed to these other processors, you're completely off your rocker. Doing so would set the kernels spinlock API in stone, which is really something you don't want to do. Not only that, but it would mean that software written for the M3 and DSP would have to know about the GPL'd spinlock layout, and I suspect that would cause major licencing headaches. In any case, Linux's spinlock API (or more accurately, the ARM exclusive access instructions) relies upon hardware coherency support (a piece of hardware called an exclusive monitor) which isn't present on the M3 nor DSP processors. So there's no way to ensure that updates from the M3 and DSP are atomic wrt the A9 updates. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
