include/asm/preempt.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef __ASM_PREEMPT_H
0003 #define __ASM_PREEMPT_H
0004
0005 #include <linux/jump_label.h>
0006 #include <linux/thread_info.h>
0007
0008 #define PREEMPT_NEED_RESCHED    BIT(32)
0009 #define PREEMPT_ENABLED (PREEMPT_NEED_RESCHED)
0010
0011 static inline int preempt_count(void)
0012 {
0013     return READ_ONCE(current_thread_info()->preempt.count);
0014 }
0015
0016 static inline void preempt_count_set(u64 pc)
0017 {
0018     /* Preserve existing value of PREEMPT_NEED_RESCHED */
0019     WRITE_ONCE(current_thread_info()->preempt.count, pc);
0020 }
0021
0022 #define init_task_preempt_count(p) do { \
0023     task_thread_info(p)->preempt_count = FORK_PREEMPT_COUNT; \
0024 } while (0)
0025
0026 #define init_idle_preempt_count(p, cpu) do { \
0027     task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
0028 } while (0)
0029
0030 static inline void set_preempt_need_resched(void)
0031 {
0032     current_thread_info()->preempt.need_resched = 0;
0033 }
0034
0035 static inline void clear_preempt_need_resched(void)
0036 {
0037     current_thread_info()->preempt.need_resched = 1;
0038 }
0039
0040 static inline bool test_preempt_need_resched(void)
0041 {
0042     return !current_thread_info()->preempt.need_resched;
0043 }
0044
0045 static inline void __preempt_count_add(int val)
0046 {
0047     u32 pc = READ_ONCE(current_thread_info()->preempt.count);
0048     pc += val;
0049     WRITE_ONCE(current_thread_info()->preempt.count, pc);
0050 }
0051
0052 static inline void __preempt_count_sub(int val)
0053 {
0054     u32 pc = READ_ONCE(current_thread_info()->preempt.count);
0055     pc -= val;
0056     WRITE_ONCE(current_thread_info()->preempt.count, pc);
0057 }
0058
0059 static inline bool __preempt_count_dec_and_test(void)
0060 {
0061     struct thread_info *ti = current_thread_info();
0062     u64 pc = READ_ONCE(ti->preempt_count);
0063
0064     /* Update only the count field, leaving need_resched unchanged */
0065     WRITE_ONCE(ti->preempt.count, --pc);
0066
0067     /*
0068      * If we wrote back all zeroes, then we're preemptible and in
0069      * need of a reschedule. Otherwise, we need to reload the
0070      * preempt_count in case the need_resched flag was cleared by an
0071      * interrupt occurring between the non-atomic READ_ONCE/WRITE_ONCE
0072      * pair.
0073      */
0074     return !pc || !READ_ONCE(ti->preempt_count);
0075 }
0076
0077 static inline bool should_resched(int preempt_offset)
0078 {
0079     u64 pc = READ_ONCE(current_thread_info()->preempt_count);
0080     return pc == preempt_offset;
0081 }
0082
0083 #ifdef CONFIG_PREEMPTION
0084
0085 void preempt_schedule(void);
0086 void preempt_schedule_notrace(void);
0087
0088 #ifdef CONFIG_PREEMPT_DYNAMIC
0089
0090 DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
0091 void dynamic_preempt_schedule(void);
0092 #define __preempt_schedule()        dynamic_preempt_schedule()
0093 void dynamic_preempt_schedule_notrace(void);
0094 #define __preempt_schedule_notrace()    dynamic_preempt_schedule_notrace()
0095
0096 #else /* CONFIG_PREEMPT_DYNAMIC */
0097
0098 #define __preempt_schedule()        preempt_schedule()
0099 #define __preempt_schedule_notrace()    preempt_schedule_notrace()
0100
0101 #endif /* CONFIG_PREEMPT_DYNAMIC */
0102 #endif /* CONFIG_PREEMPTION */
0103
0104 #endif /* __ASM_PREEMPT_H */