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.