Deep Dive into Linux task_struct: Core Data Structure for Process Management

In the Linux kernel, the task_struct structure is the central descriptor for every task (process or thread), storing all essential information throughout a task’s lifecycle.

Key fields include state (process state), pid and tgid (process and thread‑group IDs), pointers to parent ( real_parent , parent ), child and sibling lists, memory descriptor mm , file table files , scheduling entity sched_entity , and credentials cred .

The article explains how the kernel distinguishes processes from threads using pid and tgid , describes the various task states ( TASK_RUNNING , TASK_INTERRUPTIBLE , TASK_UNINTERRUPTIBLE , TASK_STOPPED , TASK_TRACED ) and exit states ( EXIT_ZOMBIE , EXIT_DEAD ), and shows the flag definitions such as PF_EXITING , PF_VCPU , PF_FORKNOEXEC .

Memory‑related members ( mm , active_mm ) and kernel‑stack handling are covered, including the layout of the kernel stack, the thread_union , and helper macros task_stack_page() and task_pt_regs() that locate a task’s stack and register state.

Finally, a simple kernel module example demonstrates iterating over all processes with for_each_process and printing each task’s pid , comm , and flags , illustrating practical access to task_struct data.