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   clone    ( 2 )

создать дочерний процесс (create a child process)

Ошибки (баги) (Bugs)

GNU C library versions 2.3.4 up to and including 2.24 contained a wrapper function for getpid(2) that performed caching of PIDs. This caching relied on support in the glibc wrapper for clone(), but limitations in the implementation meant that the cache was not up to date in some circumstances. In particular, if a signal was delivered to the child immediately after the clone() call, then a call to getpid(2) in a handler for the signal could return the PID of the calling process ("the parent"), if the clone wrapper had not yet had a chance to update the PID cache in the child. (This discussion ignores the case where the child was created using CLONE_THREAD, when getpid(2) should return the same value in the child and in the process that called clone(), since the caller and the child are in the same thread group. The stale-cache problem also does not occur if the flags argument includes CLONE_VM.) To get the truth, it was sometimes necessary to use code such as the following:

#include <syscall.h>

pid_t mypid;

mypid = syscall(SYS_getpid);

Because of the stale-cache problem, as well as other problems noted in getpid(2), the PID caching feature was removed in glibc 2.25.