Due to deficient testing, the current code doesn't return a valid result to users of sched_getaffinity(). Carry the result procmask through to the generation of result cpu mask.
Recognize Windows' limitation that if the process is multi-group (i.e., has threads in multiple cpu groups) there is no visibility to which processors in other groups are being used. One could remedy this by looping through all the process' threads, but that could be expensive so is left for future contemplation. Reported-by: Christian Franke <christian.fra...@t-online.de> Addresses: https://cygwin.com/pipermail/cygwin/2025-March/257616.html Signed-off-by: Mark Geisert <m...@maxrnd.com> Fixes: 641ecb07533e ("Cygwin: Implement sched_[gs]etaffinity()") --- winsup/cygwin/sched.cc | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/winsup/cygwin/sched.cc b/winsup/cygwin/sched.cc index 2f4fbc31a..ce1e94345 100644 --- a/winsup/cygwin/sched.cc +++ b/winsup/cygwin/sched.cc @@ -588,8 +588,11 @@ __sched_getaffinity_sys (pid_t pid, size_t sizeof_set, cpu_set_t *set) } KAFFINITY miscmask = groupmask (__get_cpus_per_group ()); + /* if process is multi-group, we don't have processor visibility. */ + if (procmask == 0) + procmask = miscmask; for (int i = 0; i < groupcount; i++) - setgroup (sizeof_set, set, grouparray[i], miscmask); + setgroup (sizeof_set, set, grouparray[i], miscmask & procmask); } else status = ESRCH; -- 2.45.1
