On Fri, 3 Feb 2012, Russell King - ARM Linux wrote: > On Thu, Feb 02, 2012 at 03:36:49PM -0800, Stephen Boyd wrote: > > On 02/02/12 13:38, Nicolas Pitre wrote: > > > What about a pair of helpers written in C instead? > > > > > > v7_flush_dcache_all() could be renamed, and a wrapper function called > > > v7_flush_dcache_all() would call the preemption disable helper, call the > > > former v7_flush_dcache_all code, then call the preemption enable helper. > > > > > > Then __v7_setup() could still call the core cache flush code without > > > issues. > > > > I tried to put the preemption disable/enable right around the place > > where it was needed. With this approach we would disable preemption > > during the entire cache flush. I'm not sure if we want to make this > > function worse for performance, do we? It certainly sounds easier than > > writing all the preempt macros in assembly though. > > Err, why do you think it's a big task? > > preempt disable is a case of incrementing the thread preempt count, while > preempt enable is a case of decrementing it, testing for zero, if zero, > then checking whether TIF_NEED_RESCHED is set and calling a function. Oh certainly. And we already do just that in a few places already. I re-read your previous email to realize that I initially misread your remark about the ickness of explicitly calling the scheduler. > If that's too much, then the simple method in assembly to quickly disable > preemption over a very few set of instructions is using mrs/msr and cpsid i. > That'll be far cheaper than fiddling about with preempt counters or > messing about with veneers in C code. Indeed. And I think that would be plenty sufficient here as the protected region is really short. I don't think that warrants any macros. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html