On Thu, Feb 23, 2012 at 1:35 PM, William Cohen <wcohen@xxxxxxxxxx> wrote: > On 02/23/2012 05:12 AM, Will Deacon wrote: >> Hi Will, >> >> On Thu, Feb 23, 2012 at 04:08:23AM +0000, William Cohen wrote: >>> >>> I was looking to see why the arm kernel builds for fedora 17 were failing with: >>> >>> arch/arm/oprofile/../../../drivers/oprofile/oprofile_perf.c:28:28: error: variably modified 'perf_events' at file scope >>> >>> The error points to the following line in oprofile_perf.c: >>> >>> static struct perf_event **perf_events[nr_cpumask_bits]; >>> >>> The nr_cpumask_bits is defined in linux/include/linux/cpumask.h with >>> the following snippet of code: >>> >>> #if NR_CPUS == 1 >>> #define nr_cpu_ids 1 >>> #else >>> extern int nr_cpu_ids; >>> #endif >>> >>> #ifdef CONFIG_CPUMASK_OFFSTACK >>> /* Assuming NR_CPUS is huge, a runtime limit is more efficient. Also, >>> * not all bits may be allocated. */ >>> #define nr_cpumask_bits nr_cpu_ids >>> #else >>> #define nr_cpumask_bits NR_CPUS >>> #endif >>> >>> The problem is that several arm machines have more than one processor >>> (CONFIG_NR_CPUS>1), making nr_cpumask_bits be a variable rather than a >>> compile time constant. Seems like the kernel should dynamically allocate >>> space for perf_events[nr_cpumask_bits] because of the variable nature >>> of nr_cpu_mask_bits. >> >> That or use NR_CPUS instead (which will be the same as nr_cpu_ids on ARM). >> >> One thing I'm curious about is why you have CONFIG_CPUMASK_OFFSTACK selected >> for the Fedora kernel? That implies you have DEBUG_PER_CPU_MAPS selected >> which, according to Kconfig, `adds a fair amount of code to kernel memory >> and decreases performance'. >> >> Cheers, >> >> Will > > When I was building kernels locally I didn't see this problem because of: > > # CONFIG_DEBUG_PER_CPU_MAPS is not set > > So adding that to the config-arm-generic of the kenrel source rpm, should be a work around for this problem. Thanks Will, I've updated the config and pushed a new build, we'll see how we get on with that. Peter _______________________________________________ arm mailing list arm@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/arm
