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

getcpu.2: Rewrite page to describe glibc wrapper function 

Since glibc 2.29, there is a wrapper for getcpu(2).
The wrapper has only 2 arguments, omitting the unused
third system call argument. Rework the manual page
to reflect this.

Reported-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2021-01-02 09:33:10 +01:00
parent 771aecbeff
commit c9eec92c18
1 changed files with 21 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
man2/getcpu.2
View File

@ -14,10 +14,10 @@
getcpu \- determine CPU and NUMA node on which the calling thread is running
.SH SYNOPSIS
.nf
.B #include <linux/getcpu.h>
.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
.B #include <sched.h>
.PP
.BI "int getcpu(unsigned int *" cpu ", unsigned int *" node \
", struct getcpu_cache *" tcache );
.BI "int getcpu(unsigned int *" cpu ", unsigned int *" node );
.fi
.SH DESCRIPTION
The
@ -37,10 +37,6 @@ or
.I node
is NULL nothing is written to the respective pointer.
.PP
The third argument to this system call is nowadays unused,
and should be specified as NULL
unless portability to Linux 2.6.23 or earlier is required (see NOTES).
.PP
The information placed in
.I cpu
is guaranteed to be current only at the time of the call:
@ -82,16 +78,31 @@ The intention of
.BR getcpu ()
is to allow programs to make optimizations with per-CPU data
or for NUMA optimization.
.\"
.SS C library/kernel differences
The kernel system call has a third argument:
.PP
.in +4n
.nf
.BI "int getcpu(unsigned int *" cpu ", unsigned int *" node ,
.BI " struct getcpu_cache *" tcache );
.fi
.in
.PP
The
.I tcache
argument is unused since Linux 2.6.24.
argument is unused since Linux 2.6.24,
and (when invoking the system call directly)
should be specified as NULL,
unless portability to Linux 2.6.23 or earlier is required.
.PP
.\" commit 4307d1e5ada595c87f9a4d16db16ba5edb70dcb1
.\" Author: Ingo Molnar <mingo@elte.hu>
.\" Date: Wed Nov 7 18:37:48 2007 +0100
.\" x86: ignore the sys_getcpu() tcache parameter
In earlier kernels,
if this argument was non-NULL,
In Linux 2.6.23 and earlier, if the
.I tcache
argument was non-NULL,
then it specified a pointer to a caller-allocated buffer in thread-local
storage that was used to provide a caching mechanism for
.BR getcpu ().