linux-進程切換核心代碼switch-to剖析

1、Linux內(nèi)核剖析之進程切換2012.10.201AT&T匯編基礎(chǔ)AT&T匯編與Intel匯編比較GCC內(nèi)聯(lián)匯編2進程切換概述_schedule()prev = rq-curr;next = pick_next_task(rq);if (likely(prev != next) context_switch(rq, prev, next);執(zhí)行進程的切換：切換頁全局目錄以安裝一個新的地址空間切換內(nèi)核態(tài)堆棧和硬件上下文3進程切換概述硬件上下文共享的CPU寄存器進程切換時，硬件上下文保存在：task_struct的類型為thread_struct的thread字段大部分寄存器，如esp,eip.內(nèi)

2、核態(tài)堆棧狀態(tài)寄存器、通用寄存器，如eax，ebx.4switch_to 宏pushflpushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipjmp _switch_to 1: popl %ebppopfl /* output parameters */ : prev_sp =m (prev-thread.sp), prev_ip =m (prev-thread.ip), =a (last) /* input parameters: */ : next_sp m (next-thread.s

3、p), next_ip m (next-thread.ip), prev a (prev), next d (next) switch_to(prev, next, last)5切換過程ABt_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infopushflpushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl $1f, %prev_ip6切換過程ABt_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infopushflpushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl

4、 $1f, %prev_ipflags7切換過程ABt_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infopushflpushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl $1f, %prev_ipflagsebp8切換過程A(prev)B(next)t_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infopushflpushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl $1f, %prev_ipflagsebpthreadesp9切換過程A(prev)B(next

5、)t_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infopushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipflagsebpebpthread spflagsthread sp完成內(nèi)核棧的切換！是不是就完成了進程的切換呢？10切換過程A(prev)B(next)t_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infomovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipjmp _switch_to1:flagseb

6、pebpthread spflagsthread sp ip11切換過程A(prev)B(next)t_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infomovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipjmp _switch_to1:flagsebpebpthread spflagsthread sp ipmovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipjmp _switch_to1:eip ip12切換過程A(prev)B(next)t_st_s內(nèi)核棧內(nèi)核棧thread_

7、infothread_infomovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipjmp _switch_to1:flagsebpebpthread spflagsthread sp ippushl %next_ipjmp _switch_to1:popl %ebppopfleip_switch_to 是一個函數(shù)！ ip return 時，將jump之前壓入棧中的元素eip賦值給eip!13switch_to(prev,next,last)last干嘛的？如果是switch_to(prev,next)：1:進程Aprev=Anext=B1:進程

8、Bprev=Bnext=other.1:進程Cprev=Cnext=Aswitch_to(A,B)switch_to(C,A)進程A恢復(fù)切換出去之前的上下文，但此時無法知道自身是由哪個進程切換來的！14switch_to 宏pushflpushl %ebpmovl %esp, %prev_spmovl %next_sp, %espmovl $1f, %prev_ippushl %next_ipjmp _switch_to 1: popl %ebppopfl /* output parameters */ : prev_sp =m (prev-thread.sp), prev_ip =m (pr

9、ev-thread.ip), =a (last), /* input parameters: */ : next_sp m (next-thread.sp), next_ip m (next-thread.ip), prev a (prev), next d (next) switch_to(prev, next, last)15switch_to(prev,next,last)A需要在切換之后保存對C的引用！switch_to(prev,next,prev) =a (last).switch_to(C,A,C)switch_to(A,B,A)1:進程Aprev=Anext=Beax=A1:進程Bprev=Bnext=othereax=Blastprev=Aeax=A1:進程Cprev=Cnext=Aeax=Ceax=Clastprev=C16切換到新建進程A(prev)B(next) - newt_st_s內(nèi)核棧內(nèi)核棧thread_infothread_infomovl %next_sp, %esp