Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

Hi Ingo, On Mon, Jul 19, 2004 at 01:59:52PM +0200, Ingo Molnar wrote: as said in a part of a previous email might_sleep() just like BUG() can be defined to noop. cond_resched() is the API to use. if you're scared that there are too many cond_resched (I'm not scared and people should enable them anyways if they make a difference, they still should be less than the number of spin_unlocks with preempt enabled), then you should add a cond_resched_costly and add a config option that turns it off. I think you don't even need to add the config option, you can define cond_resched_costly as cond_resched, and to just use it to mark the places that might be expensive. Then you should change cond_resched to call might_sleep in the else branch (as I discussed with Andrew last month). this was the core of the patch I was playing with last month which should be still valid and it solves the preprocessor issues with cond_resched (and I hope the bug was not in the below code ;) could you modify your patch accordingly? thanks! Index: linux-2.5/include/linux/kernel.h =================================================================== RCS file: /home/andrea/crypto/cvs/linux-2.5/include/linux/kernel.h,v retrieving revision 1.53 diff -u -p -r1.53 kernel.h --- linux-2.5/include/linux/kernel.h 27 Jun 2004 17:55:19 -0000 1.53 +++ linux-2.5/include/linux/kernel.h 13 Jul 2004 02:19:43 -0000 @@ -48,12 +48,23 @@ struct completion; #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP void __might_sleep(char *file, int line); #define might_sleep() __might_sleep(__FILE__, __LINE__) -#define might_sleep_if(cond) do { if (unlikely(cond)) might_sleep(); } while (0) #else #define might_sleep() do {} while(0) -#define might_sleep_if(cond) do {} while (0) #endif +#define need_resched() unlikely(test_thread_flag(TIF_NEED_RESCHED)) + +extern void __cond_resched(void); +#define cond_resched() \ +do { \ + if (need_resched()) \ + __cond_resched(); \ + else \ + might_sleep(); \ +} while (0) + +#define cond_resched_if(cond) do { if (unlikely(cond)) cond_resched(); } while (0) + #define abs(x) ({ \ int __x = (x); \ (__x < 0) ? -__x : __x; \ Index: linux-2.5/include/linux/sched.h =================================================================== RCS file: /home/andrea/crypto/cvs/linux-2.5/include/linux/sched.h,v retrieving revision 1.245 diff -u -p -r1.245 sched.h --- linux-2.5/include/linux/sched.h 2 Jul 2004 17:31:23 -0000 1.245 +++ linux-2.5/include/linux/sched.h 13 Jul 2004 02:33:12 -0000 @@ -1012,18 +1013,6 @@ static inline int signal_pending(struct { return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING)); } - -static inline int need_resched(void) -{ - return unlikely(test_thread_flag(TIF_NEED_RESCHED)); -} - -extern void __cond_resched(void); -static inline void cond_resched(void) -{ - if (need_resched()) - __cond_resched(); -} /* * cond_resched_lock() - if a reschedule is pending, drop the given lock,