55 lines
1.4 KiB
C
55 lines
1.4 KiB
C
#ifndef __ASM_PREEMPT_H
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#define __ASM_PREEMPT_H
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#include <linux/thread_info.h>
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/*
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* We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
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* that think a non-zero value indicates we cannot preempt.
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*/
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static __always_inline int preempt_count(void)
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{
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return current_thread_info()->preempt_count & ~PREEMPT_NEED_RESCHED;
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}
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static __always_inline int *preempt_count_ptr(void)
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{
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return ¤t_thread_info()->preempt_count;
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}
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/*
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* We now loose PREEMPT_NEED_RESCHED and cause an extra reschedule; however the
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* alternative is loosing a reschedule. Better schedule too often -- also this
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* should be a very rare operation.
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*/
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static __always_inline void preempt_count_set(int pc)
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{
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*preempt_count_ptr() = pc;
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}
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/*
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* We fold the NEED_RESCHED bit into the preempt count such that
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* preempt_enable() can decrement and test for needing to reschedule with a
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* single instruction.
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*
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* We invert the actual bit, so that when the decrement hits 0 we know we both
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* need to resched (the bit is cleared) and can resched (no preempt count).
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*/
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static __always_inline void set_preempt_need_resched(void)
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{
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*preempt_count_ptr() &= ~PREEMPT_NEED_RESCHED;
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}
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static __always_inline void clear_preempt_need_resched(void)
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{
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*preempt_count_ptr() |= PREEMPT_NEED_RESCHED;
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}
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static __always_inline bool test_preempt_need_resched(void)
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{
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return !(*preempt_count_ptr() & PREEMPT_NEED_RESCHED);
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}
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#endif /* __ASM_PREEMPT_H */
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