suse man page for utrace_prepare_examine

UTRACE_PREPARE_EXAMI(9) 					  utrace core API					   UTRACE_PREPARE_EXAMI(9)

NAME
       utrace_prepare_examine - prepare to examine thread state

SYNOPSIS
       int utrace_prepare_examine(struct task_struct * target, struct utrace_engine * engine, struct utrace_examiner * exam);

ARGUMENTS
       target
	   thread of interest, a struct task_struct pointer

       engine
	   engine pointer returned by utrace_attach_task

       exam
	   temporary state, a struct utrace_examiner pointer

DESCRIPTION
       This call prepares to safely examine the thread target using struct user_regset calls, or direct access to thread-synchronous fields.

       When target is current, this call is superfluous. When target is another thread, it must held stopped via UTRACE_STOP by engine.

       This call may block the caller until target stays stopped, so it must be called only after the caller is sure target is about to
       unschedule. This means a zero return from a utrace_control call on engine giving UTRACE_STOP, or a report_quiesce or report_signal callback
       to engine that used UTRACE_STOP in its return value.

       Returns -ESRCH if target is dead or -EINVAL if UTRACE_STOP was not used. If target has started running again despite UTRACE_STOP (for
       SIGKILL or a spurious wakeup), this call returns -EAGAIN.

       When this call returns zero, it's safe to use struct user_regset calls and task_user_regset_view on target and to examine some of its
       fields directly. When the examination is complete, a utrace_finish_examine call must follow to check whether it was completed safely.

Kernel Hackers Manual 2.6.					     July 2010						   UTRACE_PREPARE_EXAMI(9)