1 typedef struct spinlock { 2     union { 3         struct raw_spinlock rlock; 4  5 #ifdef CONFIG_DEBUG_LOCK_ALLOC        //忽略debug部分 6 # define LOCK_PADSIZE (offsetof(struct raw_spinlock, dep_map)) 7         struct { 8             u8 __padding[LOCK_PADSIZE]; 9             struct lockdep_map dep_map;10         };11 #endif12     };13 } spinlock_t;

 1 typedef struct raw_spinlock { 2     arch_spinlock_t raw_lock;             //arch相关结构 3 #ifdef CONFIG_GENERIC_LOCKBREAK 4     unsigned int break_lock; 5 #endif 6 #ifdef CONFIG_DEBUG_SPINLOCK 7     unsigned int magic, owner_cpu; 8     void *owner; 9 #endif10 #ifdef CONFIG_DEBUG_LOCK_ALLOC11     struct lockdep_map dep_map;12 #endif13 } raw_spinlock_t;

1 typedef struct {2     volatile unsigned int lock;3 } arch_spinlock_t;

1 static inline void spin_lock(spinlock_t *lock)2 {3     raw_spin_lock(&lock->rlock);4 }

1 #define raw_spin_lock(lock)    _raw_spin_lock(lock)

1 void __lockfunc _raw_spin_lock(raw_spinlock_t *lock)2 {3     __raw_spin_lock(lock);4 }

1 static inline void __raw_spin_lock(raw_spinlock_t *lock)2 {3     preempt_disable();                       //抢占点                          4     spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);5     LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);6 }

 1 #ifdef CONFIG_PREEMPT_COUNT               //支持才起作用，否则为空 2  3 #define preempt_disable() \ 4 do { \ 5     inc_preempt_count(); \               //增加抢占计数 6     barrier(); \                         // 7 } while (0) 8  9 #define preempt_enable_no_resched() \10 do { \11     barrier(); \12     dec_preempt_count(); \13 } while (0)14 15 #define preempt_enable() \16 do { \17     preempt_enable_no_resched(); \18     barrier(); \19     preempt_check_resched(); \20 } while (0)21 22 /* For debugging and tracer internals only! */23 #define add_preempt_count_notrace(val)            \24     do { preempt_count() += (val); } while (0)25 #define sub_preempt_count_notrace(val)            \26     do { preempt_count() -= (val); } while (0)27 #define inc_preempt_count_notrace() add_preempt_count_notrace(1)28 #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)29 30 #define preempt_disable_notrace() \31 do { \32     inc_preempt_count_notrace(); \33     barrier(); \34 } while (0)35 36 #define preempt_enable_no_resched_notrace() \37 do { \38     barrier(); \39     dec_preempt_count_notrace(); \40 } while (0)41 42 /* preempt_check_resched is OK to trace */43 #define preempt_enable_notrace() \44 do { \45     preempt_enable_no_resched_notrace(); \46     barrier(); \47     preempt_check_resched(); \48 } while (0)49 50 #else /* !CONFIG_PREEMPT_COUNT */51 52 #define preempt_disable()        do { } while (0)53 #define preempt_enable_no_resched()    do { } while (0)54 #define preempt_enable()        do { } while (0)55 56 #define preempt_disable_notrace()        do { } while (0)57 #define preempt_enable_no_resched_notrace()    do { } while (0)58 #define preempt_enable_notrace()        do { } while (0)59 60 #endif /* CONFIG_PREEMPT_COUNT */

1 #define inc_preempt_count() add_preempt_count(1)

1 # define add_preempt_count(val)    do { preempt_count() += (val); } while (0)

1 #define preempt_count()    (current_thread_info()->preempt_count)

1 /* Optimization barrier */2 /* The "volatile" is due to gcc bugs */3 #define barrier() __asm__ __volatile__("": : :"memory")

/*

如果汇编指令修改了内存，但是GCC 本身却察觉不到，因为在输出部分没有描述，

此时就需要在修改描述部分增加"memory"，告诉GCC 内存已经被修改，GCC 得知这个信息后，就会在这段指令之前，

插入必要的指令将前面因为优化Cache 到寄存器中的变量值先写回内存，如果以后又要使用这些变量再重新读取。

*/

1 #define LOCK_CONTENDED(_lock, try, lock) \2     lock(_lock)

1 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)2 {3     __acquire(lock);4     arch_spin_lock(&lock->raw_lock);5 }

1 # define __acquire(x)    __context__(x,1)  

//it's designed to test that the entry and exit contexts match, 

//and that no path through a function is ever entered with conflicting contexts. 

 1 static inline void arch_spin_lock(arch_spinlock_t *lock) 2 { 3     unsigned long tmp; 4  5     __asm__ __volatile__(               //循环测试 6 "1:    ldrex    %0, [%1]\n" 7 "    teq    %0, #0\n" 8     WFE("ne") 9 "    strexeq    %0, %2, [%1]\n"10 "    teqeq    %0, #0\n"11 "    bne    1b"12     : "=&r" (tmp)13     : "r" (&lock->lock), "r" (1)14     : "cc");15 16     smp_mb();17 }

1 #ifndef CONFIG_SMP2 #define smp_mb()    barrier()3 #define smp_rmb()    barrier()4 #define smp_wmb()    barrier()5 #else6 #define smp_mb()    dmb()7 #define smp_rmb()    dmb()8 #define smp_wmb()    dmb()9 #endif

1 static inline void __raw_spin_lock_irq(raw_spinlock_t *lock)2 {3     local_irq_disable();     //disable irq4     preempt_disable();5     spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);6     LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);7 }