Hi Alex, On 12/30/20 10:41 PM, Alejandro Colomar wrote: > The glibc wrapper doesn't provide the third argument. > Simplify the info about the (unused) kernel parameter > to the minimum that is useful. > > kernels <=2.6.23 are EOL since a long time ago. > > The old info is commented out instead of removed. I tend to be rather conservative about preserving historical detail in the manual pages. Yes, 2.6.23 may be EOL from the kernel community's point of view, but even in quite recent times I've run into folk in the embedded world that who have to at the very least support 2.6.* systems. So, as a general principle, I'm inclined to retain the kind of info that this patch removes. (I admit though that this is an extreme case: historical behavior in a system call that is not frequently used.) There are exceptions. Occassionaly I run into historical info in manual pages that is clearly wrong, or incomplete. In such cases, I am sometimes inclined to trim the details, rather than invest the effort in working out all of the historical details. Clearly though, some fix is needed, since we now have a glibc wrapper that has just two arguments. I've applied the patch below. Cheers, Michael diff --git a/man2/getcpu.2 b/man2/getcpu.2 index a75123f97..59089bd74 100644 --- a/man2/getcpu.2 +++ b/man2/getcpu.2 @@ -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@xxxxxxx> .\" 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 (). -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
