linux简单代码阅读.docx

一、 find_first_bit(2)static inline int find_first_bit(const unsigned long *vaddr, unsigned size)const unsigned long *p = vaddr;int res = 32;unsigned long num;if (!size)return 0;size = (size + 31) 5;while (!(num = *p+) if (!-size)goto out;_asm_ _volatile_ (bfffo %1#0,#0,%0 : =d (res) : d (num & -num);res = 31;out:return (long)p - (long)vaddr - 4) * 8 + res;二、 find_next_bit(2)static inline int find_next_bit(const unsigned long *vaddr, int size,int offset)const unsigned long *p = vaddr + (offset 5);int bit = offset & 31UL, res;if (offset = size)return size;if (bit) unsigned long num = *p+ & (0UL bit);offset -= bit;/* Look for one in first longword */_asm_ _volatile_ (bfffo %1#0,#0,%0 : =d (res) : d (num & -num);if (res bits);四、 _cpu_clear(2人)static inline void _cpu_clear(int cpu, volatile cpumask_t *dstp)clear_bit(cpu, dstp-bits);五、 virt_to_phys(2人)static inline unsigned long virt_to_phys(volatile void * address)return _pa(void *) address);static inline void * phys_to_virt(unsigned long address)return _va(address);六、 smp_alloc_memory(2人)/* * We are called very early to get the low memory for the * SMP bootup trampoline page. */void _init smp_alloc_memory(void)trampoline_base = (void *) alloc_bootmem_low_pages(PAGE_SIZE);/* * Has to be in very low memory so we can execute * real-mode AP code. */if (_pa(trampoline_base) = 0x9F000)BUG();/* * Make the SMP trampoline executable: */trampoline_exec = set_kernel_exec(unsigned long)trampoline_base, 1);七、 current_thread_info(2人)来自# define smp_processor_id() raw_smp_processor_id()(smp.h)/* Return a thread_info struct. */static inline struct thread_info *current_thread_info(void)struct thread_info *ti;_asm_ _volatile_ (and.d $sp, %0 : =r (ti) : 0 (8191UL);return ti;八、 cpu_idle（2人）（kernelprocess.c）Void cpu_idle(void)set_thread_flag(TIF_POLLING_NRFLAG);while (1) /* FIXME - EV6 and LCA45 know how to power down the CPU. */while (!need_resched()cpu_relax();schedule();九、 fork_idle(2人)（kernelfrok.c）task_t * _devinit fork_idle(int cpu)task_t *task;struct pt_regs regs;task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0);if (!task)return ERR_PTR(-ENOMEM);init_idle(task, cpu);unhash_process(task);return task;十、 for_each_cpu_mask(12)(kernelcpumask.h)#define for_each_cpu_mask(cpu, mask)for (cpu) = first_cpu(mask);(cpu) bits, nbits);十二、 _first_cpu(12)(kernelcpumask.h)static inline int _first_cpu(const cpumask_t *srcp, int nbits)return min_t(int, nbits, find_first_bit(srcp-bits, nbits);static inline int _next_cpu(int n, const cpumask_t *srcp, int nbits)return min_t(int, nbits, find_next_bit(srcp-bits, nbits, n+1);十三、 initialize_secondary(2 smpboot.c)/* * Everything has been set up for the secondary * CPUs - they just need to reload everything * from the task structure * This function must not return. */void _devinit initialize_secondary(void)/* * We dont actually need to load the full TSS, * basically just the stack pointer and the eip. */asm volatile(movl %0,%espntjmp *%1:r (current-thread.esp),r (current-thread.eip);十四、 alloc_cpu_id(2smpboot.c)static inline int alloc_cpu_id(void)cpumask_ttmp_map;int cpu;cpus_complement(tmp_map, cpu_present_map);cpu = first_cpu(tmp_map);if (cpu = NR_CPUS)return -ENODEV;return cpu;十五、 double_lock_balance（3人）/* * double_lock_balance - lock the busiest runqueue, this_rq is locked already. */static void double_lock_balance(runqueue_t *this_rq, runqueue_t *busiest)_releases(this_rq-lock)_acquires(busiest-lock)_acquires(this_rq-lock)if (unlikely(!spin_trylock(&busiest-lock) if (busiest lock);spin_lock(&busiest-lock);spin_lock(&this_rq-lock); elsespin_lock(&busiest-lock);十六、 cpu_isset（2人）/* No static inline type checking - see Subtlety (1) above. */#define cpu_isset(cpu, cpumask) test_bit(cpu), (cpumask).bits)十七、 spin_unlock（2人）# define spin_unlock(lock)_raw_spin_unlock(&(lock)-raw_lock)十八、 kernel_thread（3人） arch/arm/kernel/process.casm( .section .textn .alignn .type kernel_thread_helper, #functionnkernel_thread_helper:n mov r0, r1n mov lr, r3n mov pc, r2n .size kernel_thread_helper, . - kernel_thread_helpern .previous);/* * Create a kernel thread. */pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) struct pt_regs regs; memset(®s, 0, sizeof(regs); regs.ARM_r1 = (unsigned long)arg; regs.ARM_r2 = (unsigned long)fn; regs.ARM_r3 = (unsigned long)do_exit; regs.ARM_pc = (unsigned long)kernel_thread_helper | MODE_SVC26; return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);十九、 _cpu_up(2 smpboot.c)int _devinit _cpu_up(unsigned int cpu)/* In case one didnt come up */if (!cpu_isset(cpu, cpu_callin_map) printk(KERN_DEBU