Linux Process Management (1)

 

The process is during execution.ProgramAnd other resources.

 

Process passedFork ()System Call generation. This system call creates a new process by copying an existing process.Fork ()Two responses are returned for one call: one for the parent process and one for the newly created child process.

 

Process Descriptor and Task Structure

 

The kernel places the process inTask ListIn a two-way circular linked list, each of which isTask_structStructure (process descriptor ).Task_structLarge Structure (32About1.7 KContains all the information required by the kernel management process.

 

LinuxPassSlabDistributor allocationTask_structStructure to achieve Object reuse and cache coloring.

 

Each process passes throughPID. The default maximum value is32768, You can use/Proc/sys/kernel/pid_maxModify.

 

Thread_infoStructure

 

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 */

 IntPreempt_count ; /* 0 => preemptable, <0 => bug */

 

 

Mm_segment_t addr_limit ; /* Thread address space:

0-0xbfffff for user-thead

0-0xffffffff for Kernel-Thread

*/

void * sysenter_return ;

 Struct Restart_block ;

 

unsigned long previus_esp ; /* esp of the previous stack in case

Of nested (IRQ) stacks

*/

_ U8 supervisor_stack [0];

};

 

This structure is allocated at the end of the kernel stack.

 

How to find the process descriptor of the currently running process

 

 

 

Why shield 13 lower bits (when thread_size is 8192 ):

 

the stack in the kernel is from high address to low address. thread_info and kernel stack ( kernel state stack ) share the same memory , and thread_info allocation at the end of the kernel stack .