On Fri, Aug 21, 2015 at 09:50:35AM +0200, Ingo Molnar wrote: > > * Frederic Weisbecker <[email protected]> wrote: > > > > I want to have a real hook to call that says "switch to IRQ context from > > > CONTEXT_USER" or "switch to IRQ context from CONTEXT_KERNEL" (aka noop), > > > but > > > that doesn't currently exist. > > > > You're not answering _why_ you want that. > > So we'd have a comprehensive, 100% coverage, self-sufficient set of callbacks > that > track the kernel's current context state at the points where the context > switches > actually occur - not just something cobbled together heterogenously. The low > level > x86 asm code was rather messy in this area, better organization would be > welcome, > I don't think we can overdo it. > > ( I'm assuming here that it can all be done for zero or negative cost, and > that > the result will be correct and won't hurt existing users in any fashion. )
Sure, if x86 needs such a thing for internal organization it's ok, but don't do context tracking calls there. irq_enter() and irq_exit() already take care of RCU and time accounting. What Andy is doing is roughly like calling these callbacks twice for no reason. It's horrible for IRQ performances. The merge window is like tomorrow and he keeps arguing against that obvious regression instead of fixing it. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
