Line data    Source code

       1             : /* SPDX-License-Identifier: GPL-2.0 */
       2             : #ifndef __ASM_PREEMPT_H
       3             : #define __ASM_PREEMPT_H
       4             : 
       5             : #include <asm/rmwcc.h>
       6             : #include <asm/percpu.h>
       7             : #include <asm/current.h>
       8             : 
       9             : #include <linux/thread_info.h>
      10             : #include <linux/static_call_types.h>
      11             : 
      12             : /* We use the MSB mostly because its available */
      13             : #define PREEMPT_NEED_RESCHED    0x80000000
      14             : 
      15             : /*
      16             :  * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
      17             :  * that a decrement hitting 0 means we can and should reschedule.
      18             :  */
      19             : #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
      20             : 
      21             : /*
      22             :  * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
      23             :  * that think a non-zero value indicates we cannot preempt.
      24             :  */
      25             : static __always_inline int preempt_count(void)
      26             : {
      27  1881604856 :         return raw_cpu_read_4(pcpu_hot.preempt_count) & ~PREEMPT_NEED_RESCHED;
      28             : }
      29             : 
      30             : static __always_inline void preempt_count_set(int pc)
      31             : {
      32             :         int old, new;
      33             : 
      34             :         do {
      35             :                 old = raw_cpu_read_4(pcpu_hot.preempt_count);
      36             :                 new = (old & PREEMPT_NEED_RESCHED) |
      37             :                         (pc & ~PREEMPT_NEED_RESCHED);
      38             :         } while (raw_cpu_cmpxchg_4(pcpu_hot.preempt_count, old, new) != old);
      39             : }
      40             : 
      41             : /*
      42             :  * must be macros to avoid header recursion hell
      43             :  */
      44             : #define init_task_preempt_count(p) do { } while (0)
      45             : 
      46             : #define init_idle_preempt_count(p, cpu) do { \
      47             :         per_cpu(pcpu_hot.preempt_count, (cpu)) = PREEMPT_DISABLED; \
      48             : } while (0)
      49             : 
      50             : /*
      51             :  * We fold the NEED_RESCHED bit into the preempt count such that
      52             :  * preempt_enable() can decrement and test for needing to reschedule with a
      53             :  * single instruction.
      54             :  *
      55             :  * We invert the actual bit, so that when the decrement hits 0 we know we both
      56             :  * need to resched (the bit is cleared) and can resched (no preempt count).
      57             :  */
      58             : 
      59             : static __always_inline void set_preempt_need_resched(void)
      60             : {
      61             :         raw_cpu_and_4(pcpu_hot.preempt_count, ~PREEMPT_NEED_RESCHED);
      62             : }
      63             : 
      64             : static __always_inline void clear_preempt_need_resched(void)
      65             : {
      66             :         raw_cpu_or_4(pcpu_hot.preempt_count, PREEMPT_NEED_RESCHED);
      67             : }
      68             : 
      69             : static __always_inline bool test_preempt_need_resched(void)
      70             : {
      71             :         return !(raw_cpu_read_4(pcpu_hot.preempt_count) & PREEMPT_NEED_RESCHED);
      72             : }
      73             : 
      74             : /*
      75             :  * The various preempt_count add/sub methods
      76             :  */
      77             : 
      78             : static __always_inline void __preempt_count_add(int val)
      79             : {
      80          19 :         raw_cpu_add_4(pcpu_hot.preempt_count, val);
      81             : }
      82             : 
      83             : static __always_inline void __preempt_count_sub(int val)
      84             : {
      85             :         raw_cpu_add_4(pcpu_hot.preempt_count, -val);
      86             : }
      87             : 
      88             : /*
      89             :  * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
      90             :  * a decrement which hits zero means we have no preempt_count and should
      91             :  * reschedule.
      92             :  */
      93             : static __always_inline bool __preempt_count_dec_and_test(void)
      94             : {
      95          19 :         return GEN_UNARY_RMWcc("decl", pcpu_hot.preempt_count, e,
      96             :                                __percpu_arg([var]));
      97             : }
      98             : 
      99             : /*
     100             :  * Returns true when we need to resched and can (barring IRQ state).
     101             :  */
     102             : static __always_inline bool should_resched(int preempt_offset)
     103             : {
     104 27661938456 :         return unlikely(raw_cpu_read_4(pcpu_hot.preempt_count) == preempt_offset);
     105             : }
     106             : 
     107             : #ifdef CONFIG_PREEMPTION
     108             : 
     109             : extern asmlinkage void preempt_schedule(void);
     110             : extern asmlinkage void preempt_schedule_thunk(void);
     111             : 
     112             : #define preempt_schedule_dynamic_enabled        preempt_schedule_thunk
     113             : #define preempt_schedule_dynamic_disabled       NULL
     114             : 
     115             : extern asmlinkage void preempt_schedule_notrace(void);
     116             : extern asmlinkage void preempt_schedule_notrace_thunk(void);
     117             : 
     118             : #define preempt_schedule_notrace_dynamic_enabled        preempt_schedule_notrace_thunk
     119             : #define preempt_schedule_notrace_dynamic_disabled       NULL
     120             : 
     121             : #ifdef CONFIG_PREEMPT_DYNAMIC
     122             : 
     123             : DECLARE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);
     124             : 
     125             : #define __preempt_schedule() \
     126             : do { \
     127             :         __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \
     128             :         asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
     129             : } while (0)
     130             : 
     131             : DECLARE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);
     132             : 
     133             : #define __preempt_schedule_notrace() \
     134             : do { \
     135             :         __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \
     136             :         asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
     137             : } while (0)
     138             : 
     139             : #else /* PREEMPT_DYNAMIC */
     140             : 
     141             : #define __preempt_schedule() \
     142             :         asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT);
     143             : 
     144             : #define __preempt_schedule_notrace() \
     145             :         asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT);
     146             : 
     147             : #endif /* PREEMPT_DYNAMIC */
     148             : 
     149             : #endif /* PREEMPTION */
     150             : 
     151             : #endif /* __ASM_PREEMPT_H */