linux简单代码阅读

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1、一、find_first_bit(2)staticinlineintfind_first_bit(constunsignedlong*vaddr,unsignedsize){constunsignedlong*p=vaddr;intres=32;unsignedlongnum;if(!size)return0;size=(size+31)>>5;while(!(num=*p++)){if(!--size)gotoout;}__asm____volatile__("bfffo%1{#0,#0},%0":"=d"(res):"d"(num&-num));res^=31;out:return((lo

2、ng)p-(long)vaddr-4)*8+res;}二、find_next_bit(2)staticinlineintfind_next_bit(constunsignedlong*vaddr,intsize,intoffset){constunsignedlong*p=vaddr+(offset>>5);intbit=offset&31UL,res;if(offset>=size)returnsize;if(bit){unsignedlongnum=*p++&(~0UL<

3、tile__("bfffo%1{#0,#0},%0":"=d"(res):"d"(num&-num));if(res<32)returnoffset+(res^31);offset+=32;}/*Nooneyet,searchremainingfullbytesforaone*/res=find_first_bit(p,size-((long)p-(long)vaddr)*8);returnoffset+res;}一、__cpu_set(2人)(kernelcpumask.h)staticinlinevoid__cpu_set(intcpu,volatilecpumask_t*dstp){s

4、et_bit(cpu,dstp->bits);}二、__cpu_clear(2人)staticinlinevoid__cpu_clear(intcpu,volatilecpumask_t*dstp){clear_bit(cpu,dstp->bits);}三、virt_to_phys(2人)staticinlineunsignedlongvirt_to_phys(volatilevoid*address){return__pa((void*)address);}staticinlinevoid*phys_to_virt(unsignedlongaddress){return__va(addres

5、s);}四、smp_alloc_memory(2人)/**Wearecalledveryearlytogetthelowmemoryforthe*SMPbootuptrampolinepage.*/void__initsmp_alloc_memory(void){trampoline_base=(void*)alloc_bootmem_low_pages(PAGE_SIZE);/**Hastobeinverylowmemorysowecanexecute*real-modeAPcode.*/if(__pa(trampoline_base)>=0x9F000)BUG();/**MaketheSM

6、Ptrampolineexecutable:*/trampoline_exec=set_kernel_exec((unsignedlong)trampoline_base,1);}一、current_thread_info(2人)来自#definesmp_processor_id()raw_smp_processor_id()—(smp.h)/*Returnathread_infostruct.*/staticinlinestructthread_info*current_thread_info(void){structthread_info*ti;__asm____volatile__("a

7、nd.d$sp,%0":"=r"(ti):"0"(~8191UL));returnti;}二、cpu_idle（2人）（kernelprocess.c）Voidcpu_idle(void){set_thread_flag(TIF_POLLING_NRFLAG);while(1){/*FIXME--EV6andLCA45knowhowtopowerdowntheCPU.*/while(!need_