进程调度之thread_info和thread_struct

对于thread_struct

---

• 内核还需要存储每个进程的PCB信息, linux内核是支持不同体系的的, 但是不同的体系结构可能进程需要存储的信息不尽相同, 这就需要我们实现一种通用的方式, 我们将体系结构相关的部分和无关的部门进行分离

对于PPC来说，结构体如下

struct thread_struct {
	unsigned long	ksp;		/* Kernel stack pointer */
#ifdef CONFIG_PPC64
	unsigned long	ksp_vsid;
#endif
	struct pt_regs	*regs;		/* Pointer to saved register state */
	mm_segment_t	fs;		/* for get_fs() validation */
#ifdef CONFIG_PPC32
	void		*pgdir;		/* root of page-table tree */
#endif
#if defined(CONFIG_4xx) || defined (CONFIG_BOOKE)
	unsigned long	dbcr0;		/* debug control register values */
	unsigned long	dbcr1;
#endif
	double		fpr[32];	/* Complete floating point set */
	struct {			/* fpr ... fpscr must be contiguous */

		unsigned int pad;
		unsigned int val;	/* Floating point status */
	} fpscr;
	int		fpexc_mode;	/* floating-point exception mode */
	unsigned int	align_ctl;	/* alignment handling control */
#ifdef CONFIG_PPC64
	unsigned long	start_tb;	/* Start purr when proc switched in */
	unsigned long	accum_tb;	/* Total accumilated purr for process */
#endif
	unsigned long	dabr;		/* Data address breakpoint register */
#ifdef CONFIG_ALTIVEC
	/* Complete AltiVec register set */
	vector128	vr[32] __attribute((aligned(16)));
	/* AltiVec status */
	vector128	vscr __attribute((aligned(16)));
	unsigned long	vrsave;
	int		used_vr;	/* set if process has used altivec */
#endif /* CONFIG_ALTIVEC */
#ifdef CONFIG_SPE
	unsigned long	evr[32];	/* upper 32-bits of SPE regs */
	u64		acc;		/* Accumulator */
	unsigned long	spefscr;	/* SPE & eFP status */
	int		used_spe;	/* set if process has used spe */
#endif /* CONFIG_SPE */
};

而核心是如下数据结构是PPC的寄存器信息。

struct pt_regs {
	unsigned long gpr[32];
	unsigned long nip;
	unsigned long msr;
	unsigned long orig_gpr3;	/* Used for restarting system calls */
	unsigned long ctr;
	unsigned long link;
	unsigned long xer;
	unsigned long ccr;
#ifdef __powerpc64__
	unsigned long softe;		/* Soft enabled/disabled */
#else
	unsigned long mq;		/* 601 only (not used at present) */
					/* Used on APUS to hold IPL value. */
#endif
	unsigned long trap;		/* Reason for being here */
	/* N.B. for critical exceptions on 4xx, the dar and dsisr
	   fields are overloaded to hold srr0 and srr1. */
	unsigned long dar;		/* Fault registers */
	unsigned long dsisr;		/* on 4xx/Book-E used for ESR */
	unsigned long result;		/* Result of a system call */
};

对于X86来说，定义则依赖于X86的CPU实现

struct thread_struct {
/* cached TLS descriptors. */
	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;
/* Hardware debugging registers */
	unsigned long	debugreg[8];  /* %%db0-7 debug registers */
/* fault info */
	unsigned long	cr2, trap_no, error_code;
/* floating point info */
	union i387_union	i387;
/* virtual 86 mode info */
	struct vm86_struct __user * vm86_info;
	unsigned long		screen_bitmap;
	unsigned long		v86flags, v86mask, saved_esp0;
	unsigned int		saved_fs, saved_gs;
/* IO permissions */
	unsigned long	*io_bitmap_ptr;
 	unsigned long	iopl;
/* max allowed port in the bitmap, in bytes: */
	unsigned long	io_bitmap_max;
};

该结构体处于进程数据结构里面：

struct task_struct

    thread_struct thread;

 

 

对于thread_info

---

• 内核栈跟thread_info共用结构体

用一种通用的方式来描述进程, 这就是struct task_struct, 而thread_info就保存了特定体系结构的汇编代码段需要访问的那部分进程的数据,我们在thread_info中嵌入指向task_struct的指针, 则我们可以很方便的通过thread_info来查找task_struct

struct thread_info {
	struct task_struct	*task;		/* main task structure */
	struct exec_domain	*exec_domain;	/* execution domain */
	unsigned long		flags;		/* low level flags */
	unsigned long		status;		/* thread-synchronous flags */
	__u32			cpu;		/* current CPU */
	int			preempt_count;	/* 0 => preemptable, <0 => BUG */


	mm_segment_t		addr_limit;	/* thread address space:
					 	   0-0xBFFFFFFF for user-thead
						   0-0xFFFFFFFF for kernel-thread
						*/
	void			*sysenter_return;
	struct restart_block    restart_block;

	unsigned long           previous_esp;   /* ESP of the previous stack in case
						   of nested (IRQ) stacks
						*/
	__u8			supervisor_stack[0];
};

union thread_union {
	struct thread_info thread_info;
	unsigned long stack[THREAD_SIZE/sizeof(long)];
};

该结构体在task_struct的位置如下：

看一下这个函数就明白了

static struct task_struct *dup_task_struct(struct task_struct *orig)
{
	struct task_struct *tsk;
	struct thread_info *ti;//声明

	prepare_to_copy(orig);

	tsk = alloc_task_struct();
	if (!tsk)
		return NULL;

	ti = alloc_thread_info(tsk);//分配空间
	if (!ti) {
		free_task_struct(tsk);
		return NULL;
	}

	*tsk = *orig;
	tsk->stack = ti;//与task_struct关联
	setup_thread_stack(tsk, orig);

#ifdef CONFIG_CC_STACKPROTECTOR
	tsk->stack_canary = get_random_int();
#endif

	/* One for us, one for whoever does the "release_task()" (usually parent) */
	atomic_set(&tsk->usage,2);
	atomic_set(&tsk->fs_excl, 0);
#ifdef CONFIG_BLK_DEV_IO_TRACE
	tsk->btrace_seq = 0;
#endif
	tsk->splice_pipe = NULL;
	return tsk;
}

 

 

 

 

Linux进程内核栈与thread_info结构详解--Linux进程的管理与调度（九）

http://blog.youkuaiyun.com/gatieme/article/details/51577479

Linux下0号进程的前世(init_task进程)今生(idle进程)----Linux进程的管理与调度（五）
https://blog.youkuaiyun.com/gatieme/article/details/51484562

Linux内核分析（八）：Linux进程调度的时机和进程切换
https://blog.youkuaiyun.com/u013291303/article/details/70199645

Linux内核分析（六）：进程的描述和进程的创建
https://blog.youkuaiyun.com/u013291303/article/details/68954599
 

进程内核栈、用户栈
https://blog.youkuaiyun.com/bailyzheng/article/details/8015618