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0102874755
We need a few special preempt_count accessors: - task_preempt_count() for when we're interested in the preemption count of another (non-running) task. - init_task_preempt_count() for properly initializing the preemption count. - init_idle_preempt_count() a special case of the above for the idle threads. With these no generic code ever touches thread_info::preempt_count anymore and architectures could choose to remove it. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
69 lines
1.8 KiB
C
69 lines
1.8 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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* must be macros to avoid header recursion hell
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*/
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#define task_preempt_count(p) \
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(task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED)
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#define init_task_preempt_count(p) do { \
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task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
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} while (0)
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#define init_idle_preempt_count(p, cpu) do { \
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task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \
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} while (0)
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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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