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Similar a プロセスとコンテキストスイッチ
Similar a プロセスとコンテキストスイッチ (20)
プロセスとコンテキストスイッチ
- 6. // include/linux/sched.h struct task_struct { volatile long state; /* -1 unrunnable, 0 runnable, >0 stop struct thread_info *thread_info; atomic_t usage; unsigned long flags; /* per process flags, defined below * int prio, static_prio; struct list_head run_list; prio_array_t *array; struct list_head tasks; struct mm_struct *mm, *active_mm;
- 7. /* * pointers to (original) parent process, youngest child, yo * older sibling, respectively. (p->father can be replaced * p->parent->pid) */ struct task_struct *real_parent; /* real parent process (wh struct task_struct *parent; /* parent process */ /* ipc stuff */ struct thread_struct thread; /* filesystem information */ struct fs_struct *fs; /* open file information */ struct files_struct *files; /* namespace */ struct signal_struct *signal; struct sigpending pending; };
- 8. スレッド情報とカーネルスタック カーネルがプロセスに対して割り振る8KB(2Pages)の領域で、先頭にス レッド情報である thread_info 構造体、末尾にはカーネル用のスタッ クを配置する。
- 10. // include/linux/sched.h union thread_union { struct thread_info thread_info; unsigned long stack[THREAD_SIZE/sizeof(long)]; };
- 11. // include/asm-i386/thread_info.h struct thread_info { struct task_struct *task; /* main task st struct exec_domain *exec_domain; /* execution do unsigned long flags; /* low level fl unsigned long status; /* thread-synch __u32 cpu; /* current CPU __s32 preempt_count; /* 0 => preempta mm_segment_t addr_limit; /* thread addre 0-0xBFFFFFFF 0-0xFFFFFFFF */ struct restart_block restart_block; unsigned long previous_esp; /* ESP of the p of nested (I */ __u8 supervisor_stack[0]; };
- 12. 余談➀ カレントプロセスの取得方法。 #define current get_current() static inline struct task_struct * get_current(void) { return current_thread_info()->task; } #define THREAD_SIZE (8192) static inline struct thread_info *current_thread_info(void) { struct thread_info *ti; __asm__("andl %%esp,%0; " :"=r" (ti) : "0" (~(THREAD_SIZE - 1)) ); return ti; }
- 13. TSS(TaskStateSegment) タスク(プロセス)の状態を保持するセグメント。Linuxでは主にI/Oポート へのアクセス権限を保持するビットマップなどを保持する。各CPUに1 つずつ保持する。 // include/asm-i386/processor.h struct tss_struct { unsigned short back_link,__blh; unsigned long esp0; unsigned short ss0,__ss0h; unsigned long esp1; unsigned short ss1,__ss1h; /* ss1 is used to cache MSR_I unsigned long esp2; unsigned short ss2,__ss2h; unsigned long __cr3;
- 14. unsigned long eip; unsigned long eflags; unsigned long eax,ecx,edx,ebx; unsigned long esp; unsigned long ebp; unsigned long esi; unsigned long edi; unsigned short es, __esh; unsigned short cs, __csh; unsigned short ss, __ssh; unsigned short ds, __dsh; unsigned short fs, __fsh; unsigned short gs, __gsh; unsigned short ldt, __ldth; unsigned short trace, io_bitmap_base;
- 15. /* * The extra 1 is there because the CPU will access an * additional byte beyond the end of the IO permission * bitmap. The extra byte must be all 1 bits, and must * be within the limit. */ unsigned long io_bitmap[IO_BITMAP_LONGS + 1]; /* * Cache the current maximum and the last task that used the */ unsigned long io_bitmap_max; struct thread_struct *io_bitmap_owner; /* * pads the TSS to be cacheline-aligned (size is 0x100) */ unsigned long __cacheline_filler[35]; /* * .. and then another 0x100 bytes for emergency kernel stac */ unsigned long stack[64]; } __attribute__((packed));
- 16. 余談➁ IntelのTSSという形式規定。 TSSは元々タスク毎に存在し、その状態を保持するセグメント（これが 本来のTSSの在り方）。 TSSを用いてタスクスイッチが行われるOSでは far jmp (セグメント間 のジャンプ命令)の1命令のみでハードウェア的にタスクスイッチに必要 な処理が走る。 e.g. jmp 0048:00000000
- 17. 余談➁~続き~
- 20. // include/asm-i386/processor.h struct thread_struct { struct desc_struct tls_array[GDT_ENTRY_TLS_ENTRIES]; unsigned long esp0; unsigned long sysenter_cs; unsigned long eip; unsigned long esp; unsigned long fs; unsigned long gs; unsigned long debugreg[8]; /* %%db0-7 debug registers */ unsigned long cr2, trap_no, error_code; union i387_union i387; struct vm86_struct __user * vm86_info; unsigned long screen_bitmap; unsigned long v86flags, v86mask, saved_esp0; unsigned int saved_fs, saved_gs; unsigned long *io_bitmap_ptr; unsigned long io_bitmap_max; };
- 22. // kernel/sched.c /* * schedule() is the main scheduler function. */ asmlinkage void __sched schedule(void) { long *switch_count; task_t *prev, *next; runqueue_t *rq; prio_array_t *array; struct list_head *queue; unsigned long long now; unsigned long run_time; int cpu, idx; :
- 23. static inline task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next) { struct mm_struct *mm = next->mm; struct mm_struct *oldmm = prev->active_mm; if (unlikely(!mm)) { next->active_mm = oldmm; atomic_inc(&oldmm->mm_count); enter_lazy_tlb(oldmm, next); } else switch_mm(oldmm, mm, next); if (unlikely(!prev->mm)) { prev->active_mm = NULL; WARN_ON(rq->prev_mm); rq->prev_mm = oldmm; } switch_to(prev, next, prev); return prev; }
- 25. // include/asm-i386/mmu_context.h static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk) { : /* Re-load page tables */ load_cr3(next->pgd); : } // include/asm-i386/processor.h #define load_cr3(pgdir) asm volatile("movl %0,%%cr3": :"r" (__pa(pgdir)))
- 26. カーネルモードスタックとハードウェアコン テキストの切り替え // include/asm-i386/system.h #define switch_to(prev,next,last) do { unsigned long esi,edi; asm volatile("pushfl" "pushl %%ebp" "movl %%esp,%0" /* save ESP */ "movl %5,%%esp" /* restore ESP */ "movl $1f,%1" /* save EIP */ "pushl %6" /* restore EIP */ "jmp __switch_to" "1:" "popl %%ebp" "popfl" :"=m" (prev->thread.esp), "=m" (prev->thread.eip), "=a" (last),"=S" (esi),"=D" (edi) :"m" (next->thread.esp), "m" (next->thread.eip), "2" (prev), "d" (next)); } while (0)
- 27. // archi386kernelprocess.c struct task_struct fastcall * __switch_to(struct task_struct { struct thread_struct *prev = &prev_p->thread, *next = &next_p->thread; int cpu = smp_processor_id(); struct tss_struct *tss = &per_cpu(init_tss, cpu); : __unlazy_fpu(prev_p); : if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr)) handle_io_bitmap(next, tss); return prev_p; } // includeasm-i386linkage.h #define fastcall __attribute__((regparm(3)))