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. -Will _______________________________________________ arm mailing list arm@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/arm
