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原帖由 flw 于 2007-8-14 10:35 发表 ![]()
to coldwarm:
你的观点也是错的。
麻烦老大指出来哪里有问题。
- kernel/sched.c
- 1048 /*
- 1049 * context_switch - switch to the new MM and the new
- 1050 * thread's register state.
- 1051 */
- 1052 static inline
- 1053 task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next)
- 1054 {
- 1055 struct mm_struct *mm = next->mm;
- 1056 struct mm_struct *oldmm = prev->active_mm;
- ...
- 1063 switch_mm(oldmm, mm, next);
- ...
- 1072 switch_to(prev, next, prev);
- 1073
- 1074 return prev;
- 1075 }
- /include/asm-i386/mmu_context.h
- 026 static inline void switch_mm(struct mm_struct *prev,
- 027 struct mm_struct *next,
- 028 struct task_struct *tsk)
- 029 {
- 030 int cpu = smp_processor_id();
- 031
- 032 if (likely(prev != next)) {
- 033 /* stop flush ipis for the previous mm */
- 034 cpu_clear(cpu, prev->cpu_vm_mask);
- 035 #ifdef CONFIG_SMP
- 036 cpu_tlbstate[cpu].state = TLBSTATE_OK;
- 037 cpu_tlbstate[cpu].active_mm = next;
- 038 #endif
- 039 cpu_set(cpu, next->cpu_vm_mask);
- 040
- 041 /* Re-load page tables */
- 042 load_cr3(next->pgd);
- 043
- 044 /*
- 045 * load the LDT, if the LDT is different:
- 046 */
- 047 if (unlikely(prev->context.ldt != next->context.ldt))
- 048 load_LDT_nolock(&next->context, cpu);
- 049 }
- 050 #ifdef CONFIG_SMP
- 051 else {
- /include/asm-i386/system.h
- 012 extern struct task_struct * FASTCALL(__switch_to(struct task_struct *prev, struct
- task_struct *next));
- 015 #define switch_to(prev,next,last) do { \
- 016 unsigned long esi,edi; \
- 017 asm volatile("pushfl\n\t" \
- 018 "pushl %%ebp\n\t" \
- 019 "movl %%esp,%0\n\t" /* save ESP */ \
- 020 "movl %5,%%esp\n\t" /* restore ESP */ \
- 021 "movl $1f,%1\n\t" /* save EIP */ \
- 022 "pushl %6\n\t" /* restore EIP */ \
- 023 "jmp __switch_to\n" \
- 023 "1:\t" \
- 024 "popl %%ebp\n\t" \
- 025 "popfl" \
- 026 :"=m" (prev->thread.esp),"=m" (prev->thread.eip), \
- 027 "=a" (last),"=S" (esi),"=D" (edi) \
- 028 :"m" (next->thread.esp),"m" (next->thread.eip), \
- 029 "2" (prev), "d" (next)); \
- 030 } while (0)
这段是上下文切换的代码。它保存的只是对任务的当前状态的描述。从操作系统的角度来看，在这个层次上，它所认知的单位仅仅是页面，至于页面上到底存放的是什么，它根本就不知道，那只能由应用程序来解释。 |
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楼主: escapedog
发表于 2007-08-14 10:12
发表于 2007-08-14 10:35
