On 1/2/21 9:41 AM, Michael Kerrisk (man-pages) wrote: > 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. Hi Michael, Agreed :-) Cheers, Alex > > 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 (). > -- Alejandro Colomar Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ http://www.alejandro-colomar.es/
