CURPROC(9)

CURPROC(9) | Kernel Developer's Manual | CURPROC(9)

# NAME

`curcpu`, `curlwp`, `curproc` — current processor, thread, and process

# SYNOPSIS

`#include <sys/proc.h>`

struct cpu_info *
`curcpu`(void);

struct proc *curproc;
struct lwp *curlwp;

`#include <sys/cpu.h>`

bool
`curcpu_stable`(void);

# DESCRIPTION

The following retrieve the current CPU, process, and thread (lightweight process, or LWP), respectively:

`curcpu`()
  Returns a pointer to the struct cpu_info structure representing the CPU that the code calling it is running on.

  The value of `curcpu`() is unstable and may be stale as soon as it is read unless the caller prevents preemption by raising the IPL (spl(9), mutex(9)), by disabling preemption (kpreempt_disable(9)), or by binding the thread to its CPU (curlwp_bind(9)).

  The function `curcpu_stable`() can be used in assertions (KASSERT(9)) to verify that `curcpu`() is stable in the current context. `curcpu_stable`() MUST NOT be used to make dynamic decisions about whether to query `curcpu`().

`curproc`
  Yields a pointer to the struct proc structure representing the currently running process.

  The value of `curproc` is stable and does not change during execution except in machine-dependent logic to perform context switches, so it works like a global constant, not like a stateful procedure.

`curlwp`
  Yields a pointer to the struct lwp structure representing the currently running thread.

  The value of `curlwp` is stable and does not change during execution except in machine-dependent logic to perform context switches, so it works like a global constant, not like a stateful procedure.

# SOURCE REFERENCES

The `curcpu`() macro is defined in the machine-independent machine/cpu.h.

The `curproc` macro is defined in sys/lwp.h.

The `curlwp` macro has a machine-independent definition in sys/lwp.h, but it may be overridden by machine/cpu.h, and must be overridden on architectures supporting multiprocessing and kernel preemption.

The `curcpu_stable`() function is defined in kern/subr_cpu.c.

# SEE ALSO

cpu_number(9), proc_find(9)

July 8, 2023 | NetBSD 11.0