cpu_lwp_fork(9) - NetBSD Manual Pages

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CPU_LWP_FORK(9)        NetBSD Kernel Developer's Manual        CPU_LWP_FORK(9)

cpu_lwp_fork, child_return, lwp_trampoline -- finish a fork operation
#include <sys/proc.h> void cpu_lwp_fork(struct lwp *l1, struct lwp *l2, void *stack, size_t stacksize, void (*func)(void *), void *arg); void child_return(void *arg);
cpu_lwp_fork() is the machine-dependent portion of fork1() which finishes a fork operation, with child lwp l2 nearly set up. It copies and updates the PCB and trap frame from the parent l1, making the child ready to run. cpu_lwp_fork() rigs the child's kernel stack so that it will start in lwp_trampoline(). lwp_trampoline() does not have a normal calling sequence and is entered by cpu_switchto(). If an alternate user-level stack is requested (with non-zero values in both the stack and stacksize arguments), the user stack pointer is set up accordingly. After being entered by cpu_switchto() and while running in user context (within the kernel) lwp_trampoline() will invoke the function func with the argument arg. If a kernel thread is being created, the return path and argument are specified with func and arg. If a user process is being created, fork1() will pass child_return() and l2 to cpu_lwp_fork() as func and arg respectively. This causes the newly-created child process to go directly to user level with an apparent return value of 0 from fork(2), while the parent process returns normally.
fork(2), cpu_switchto(9), fork1(9) NetBSD 10.99 April 26, 2018 NetBSD 10.99
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