On Thu, Dec 20, 2001 at 11:41:38AM +0000, John Levon wrote: > On Wed, Dec 19, 2001 at 11:07:11AM +0530, Bharata B Rao wrote: > > > Please consider the following definitions from include/linux/irq_cpustat.h > > -------------------------- > > #ifdef CONFIG_SMP > > #define __IRQ_STAT(cpu, member) (irq_stat[cpu].member) > > #else > > #define __IRQ_STAT(cpu, member) ((void)(cpu), irq_stat[0].member) > > #endif > > I can only assume this is for performance. cpu might not be constant to the compiler, > so the first would still have an indirection overhead on UP. The second one, however, > lets the compiler optimise as the value of cpu is discarded (assume its evaluation has > not side effects that is ;) If that is so, why not just #define __IRQ_STAT(cpu, member) (irq_stat[0].member) for UP, so that the macros like local_irq_count(cpu) can be used as Lvalue. (I am concerned about not being able to use this as Lvalue in UP) Regards, Bharata. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ IRC Channel: irc.openprojects.net / #kernelnewbies Web Page: http://www.kernelnewbies.org/
