On Thu, 9 Sep 2010 18:55:12 -0700 Drew <drew.kay@xxxxxxxxx> wrote: > Hi, > > I was going through the raid6 code in 2.6.35 and I came across an > empty function definition for cpu_relax() in include/linux/raid/pq.h > (line 135) that appears to be called in drivers/md/raid6algos.c (line > 113). My C code skills are a bit rusty but I'm assuming the > cpu_relax() call in raid6algos.c uses the definition in pq.h. > > If so, why is cpu_relax() in pq.h an empty function when there's > already a definition for cpu_relax() in > arch/x86/include/asm/processor.h? > > Conversely, if the cpu_relax() function call in raid6algos.c uses the > definition in processor.h, why do we have a second definition in pq.h? > > It strikes me that if the purpose of cpu_relax() is to signal the > kernel that we're not doing anything, why create our own empty > function when there's already one that is correct across all supported > architectures? > That is inside #ifndef __KERNEL__ #endif and so is not used when compiling the kernel. It is used when compiling the same code into a user-space test program. Thanks for the review though. NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
