Hi Christian,
On 3/8/2025 9:11 AM, Christian Franke via Cygwin wrote:
Testcase:
$ grep processor /proc/cpuinfo | tail -1 # i7-14700K
processor : 27
$ sleep 60 & taskset 0x1 sleep 60 &
[1] 62094
[2] 62095
$ taskset -p 62094
pid 62094's current affinity mask: fffffff
$ taskset -p 62095
pid 62095's current affinity mask: fffffff
Another test shows that the affinity mask is correctly set to 0x1 by
sched_setaffinity().
In sched.cc:__sched_getaffinity_sys(), GetProcessAffinityMask() is
called, but its 'procmask' result is never used. The returned cpu_set is
build using groupmask(__get_cpus_per_group ()) which is constant, here
0xfffffff. The original commit 641ecb07 likely worked (until 687c4bad^)
on older Windows versions which did not support cpu groups.
I don't know how to fix this for systems with more than one cpu group,
so no patch provided.
It might be needed to handle interesting corner cases: "If the process
had explicitly set the affinity of one or more of its threads outside of
the process' primary group, the function returns zero for both affinity
masks."
https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-
getprocessaffinitymask
Thanks very much for the report and diagnosis. I will investigate shortly.
..mark
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