On Thu, Feb 02, 2012 at 03:36:49PM -0800, Stephen Boyd wrote: > On 02/02/12 13:38, Nicolas Pitre wrote: > > On Thu, 2 Feb 2012, Russell King - ARM Linux wrote > >> On Thu, Feb 02, 2012 at 11:24:46AM -0800, Stephen Boyd wrote: > >>> Should we move get_thread_info into assembler.h? It seems odd > >>> to include entry-header.S but I saw that vfp was doing the same. > >> Probably yes, and probably also have preempt_disable and preempt_enable > >> assembler macros. That's going to get rather icky if we have to > >> explicitly call the scheduler though (to solve (1)). > > 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. 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. -- 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