On Thu April 5 2007 3:08 pm, Arnd Bergmann wrote: > On Thursday 05 April 2007, Kevin Corry wrote: > > First, the stock 2.6.20 kernel has a prototype in include/linux/smp.h for > > a function called smp_call_function_single(). However, this routine is > > only implemented on i386, x86_64, ia64, and mips. Perfmon2 apparently > > needs to call this to run a function on a specific CPU. Powerpc provides > > an smp_call_function() routine to run a function on all active CPUs, so I > > used that as a basis to add an smp_call_function_single() routine. I've > > included the patch below and was wondering if it looked like a sane > > approach. > > The function itself looks good, but since it's very similar to the existing > smp_call_function(), you should probably try to share some of the code, > e.g. by making a helper function that gets an argument to decide whether > to run on a specific CPU or on all CPUs.
Ok. I'll see what I can come up with and post another patch today or tomorrow. > > Next, we ran into a problem related to Perfmon2 initialization and sysfs. > > The problem turned out to be that the powerpc version of topology_init() > > is defined as an __initcall() routine, but Perfmon2's initialization is > > done as a subsys_initcall() routine. Thus, Perfmon2 tries to initialize > > its sysfs information before some of the powerpc cpu information has been > > initialized. However, on all other architectures, topology_init() is > > defined as a subsys_initcall() routine, so this problem was not seen on > > any other platforms. Changing the powerpc version of topology_init() to a > > subsys_initcall() seems to have fixed the bug. However, I'm not sure if > > that is going to cause problems elsewhere in the powerpc code. I've > > included the patch below (after the smp-call-function-single patch). Does > > anyone know if this change is safe, or if there was a specific reason > > that topology_init() was left as an __initcall() on powerpc? > > In general, it's better to do initcalls as late as possible, so > __initcall() is preferred over subsys_initcall() if both work. Have you > tried doing it the other way and starting perfmon2 from a regular > __initcall()? For the moment, I made the change to topology_init() since it was the simplest fix to get things working. I have considered switching the perfmon2 initialization to __initcall(), but there are apparently some timing issues with ensuring that the perfmon2 core code is initialized before any of its sub-modules. Since they could all be compiled statically in the kernel, I'm not sure if there's a way to ensure the ordering of calls within a single initcall level. I'll need to ask Stephane if there were any other reasons why subsys_initcall() was used for perfmon2. Thanks, Arnd. -- Kevin Corry [EMAIL PROTECTED] http://www.ibm.com/linux/ - 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/
