LDP
/
man-pages
mirror of https://github.com/mkerrisk/man-pages
0
1
Fork 0
Code Releases Activity

clone.2: Update BUGS to reflect fact that PID caching was removed in glibc 2.25 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2017-07-13 07:21:08 +02:00
parent 9338d37b76
commit abcf3b1db9
1 changed files with 15 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
man2/clone.2
View File

@ -1183,22 +1183,22 @@ On i386,
should not be called through vsyscall, but directly through
.IR "int $0x80" .
.SH BUGS
Versions of the GNU C library that include the NPTL threading library
contain a wrapper function for
GNU C library versions 2.3.4 up to and including 2.24
contained a wrapper function for
.BR getpid (2)
that performs caching of PIDs.
This caching relies on support in the glibc wrapper for
that performed caching of PIDs.
This caching relied on support in the glibc wrapper for
.BR clone (),
but as currently implemented,
the cache may not be up to date in some circumstances.
but limitations in the implementation
meant that the cache was not up to date in some circumstances.
In particular,
if a signal is delivered to the child immediately after the
if a signal was delivered to the child immediately after the
.BR clone ()
call, then a call to
.BR getpid (2)
in a handler for the signal may return the PID
in a handler for the signal could return the PID
of the calling process ("the parent"),
if the clone wrapper has not yet had a chance to update the PID
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
.BR CLONE_THREAD ,
@ -1212,9 +1212,9 @@ The stale-cache problem also does not occur if the
.I flags
argument includes
.BR CLONE_VM .)
To get the truth, it may be necessary to use code such as the following:
To get the truth, it was sometimes necessary to use code such as the following:
.PP
.nf
#include <syscall.h>
pid_t mypid;
@ -1224,6 +1224,10 @@ To get the truth, it may be necessary to use code such as the following:
.\" See also the following bug reports
.\" https://bugzilla.redhat.com/show_bug.cgi?id=417521
.\" http://sourceware.org/bugzilla/show_bug.cgi?id=6910
.PP
Because of the stale-cache problem, as well as other problems noted in
.BR getpid (2),
the PID caching feature was removed in glibc 2.25.
.SH EXAMPLE
The following program demonstrates the use of
.BR clone ()