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4ad87eee54
In order to use preempt_count() to track the interrupt disable nesting
level, __preempt_count_{add,sub}_return() are introduced, as their names
suggest, these primitives return the new value of the preempt_count()
after changing it. The following example shows the usage of it in
local_interrupt_disable():
// increase the HARDIRQ_DISABLE bit
new_count = __preempt_count_add_return(HARDIRQ_DISABLE_OFFSET);
// if it's the first-time increment, then disable the interrupt
// at hardware level.
if ((new_count & HARDIRQ_DISABLE_MASK) == HARDIRQ_DISABLE_OFFSET) {
local_irq_save(flags);
raw_cpu_write(local_interrupt_disable_state, flags);
}
Having these primitives will avoid a read of preempt_count() after
changing preempt_count() on certain architectures.
Signed-off-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # s390
Link: https://patch.msgid.link/20260804161447.84806-4-boqun@kernel.org
115 lines
2.6 KiB
C
115 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#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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#define PREEMPT_ENABLED (0)
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static __always_inline int preempt_count(void)
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{
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return READ_ONCE(current_thread_info()->preempt_count);
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}
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static __always_inline volatile 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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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 init_task_preempt_count(p) do { \
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task_thread_info(p)->preempt_count = FORK_PREEMPT_COUNT; \
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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_DISABLED; \
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} while (0)
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static __always_inline void set_preempt_need_resched(void)
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{
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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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}
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static __always_inline bool test_preempt_need_resched(void)
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{
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return false;
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}
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/*
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* The various preempt_count add/sub methods
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*/
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static __always_inline void __preempt_count_add(int val)
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{
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*preempt_count_ptr() += val;
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}
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static __always_inline void __preempt_count_sub(int val)
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{
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*preempt_count_ptr() -= val;
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}
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static __always_inline int __preempt_count_add_return(int val)
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{
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*preempt_count_ptr() += val;
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return *preempt_count_ptr();
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}
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static __always_inline int __preempt_count_sub_return(int val)
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{
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*preempt_count_ptr() -= val;
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return *preempt_count_ptr();
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}
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static __always_inline bool __preempt_count_dec_and_test(void)
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{
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/*
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* Because of load-store architectures cannot do per-cpu atomic
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* operations; we cannot use PREEMPT_NEED_RESCHED because it might get
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* lost.
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*/
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return !--*preempt_count_ptr() && tif_need_resched();
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}
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/*
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* Returns true when we need to resched and can (barring IRQ state).
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*/
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static __always_inline bool should_resched(int preempt_offset)
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{
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return unlikely(preempt_count() == preempt_offset &&
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tif_need_resched());
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}
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#ifdef CONFIG_PREEMPTION
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extern asmlinkage void preempt_schedule(void);
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extern asmlinkage void preempt_schedule_notrace(void);
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#if defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
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void dynamic_preempt_schedule(void);
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void dynamic_preempt_schedule_notrace(void);
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#define __preempt_schedule() dynamic_preempt_schedule()
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#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace()
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#else /* !CONFIG_PREEMPT_DYNAMIC || !CONFIG_HAVE_PREEMPT_DYNAMIC_KEY*/
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#define __preempt_schedule() preempt_schedule()
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#define __preempt_schedule_notrace() preempt_schedule_notrace()
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#endif /* CONFIG_PREEMPT_DYNAMIC && CONFIG_HAVE_PREEMPT_DYNAMIC_KEY*/
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#endif /* CONFIG_PREEMPTION */
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#endif /* __ASM_PREEMPT_H */
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