From a787870924dbd6f321661e06d4ec1c7a408c9ccf Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 14 Aug 2013 14:55:40 +0200 Subject: sched, arch: Create asm/preempt.h In order to prepare to per-arch implementations of preempt_count move the required bits into an asm-generic header and use this for all archs. Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-h5j0c1r3e3fk015m30h8f1zx@git.kernel.org Signed-off-by: Ingo Molnar --- include/asm-generic/preempt.h | 54 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 include/asm-generic/preempt.h (limited to 'include/asm-generic') diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h new file mode 100644 index 000000000000..a1fc6590a743 --- /dev/null +++ b/include/asm-generic/preempt.h @@ -0,0 +1,54 @@ +#ifndef __ASM_PREEMPT_H +#define __ASM_PREEMPT_H + +#include + +/* + * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users + * that think a non-zero value indicates we cannot preempt. + */ +static __always_inline int preempt_count(void) +{ + return current_thread_info()->preempt_count & ~PREEMPT_NEED_RESCHED; +} + +static __always_inline int *preempt_count_ptr(void) +{ + return ¤t_thread_info()->preempt_count; +} + +/* + * We now loose PREEMPT_NEED_RESCHED and cause an extra reschedule; however the + * alternative is loosing a reschedule. Better schedule too often -- also this + * should be a very rare operation. + */ +static __always_inline void preempt_count_set(int pc) +{ + *preempt_count_ptr() = pc; +} + +/* + * We fold the NEED_RESCHED bit into the preempt count such that + * preempt_enable() can decrement and test for needing to reschedule with a + * single instruction. + * + * We invert the actual bit, so that when the decrement hits 0 we know we both + * need to resched (the bit is cleared) and can resched (no preempt count). + */ + +static __always_inline void set_preempt_need_resched(void) +{ + *preempt_count_ptr() &= ~PREEMPT_NEED_RESCHED; +} + +static __always_inline void clear_preempt_need_resched(void) +{ + *preempt_count_ptr() |= PREEMPT_NEED_RESCHED; +} + +static __always_inline bool test_preempt_need_resched(void) +{ + return !(*preempt_count_ptr() & PREEMPT_NEED_RESCHED); +} + +#endif /* __ASM_PREEMPT_H */ -- cgit v1.2.3