More flexible test affinity setting (#44677)

* More flexibly test affinity setting

When running on a machine with `cpusets` applied, we are unable to
assign CPU affinity to CPUs 1 and 2; we may be locked to CPUs 9-16, for
example.  So we must inspect what our current cpumask is, and from that
select CPUs that we can safely assign affinity to in our tests.

* Import `uv_thread_getaffinity` from `print_process_affinity.jl`

* Call `uv_thread_getaffinity` only if `AFFINITY_SUPPORTED`

* Fix a syntax error

Co-authored-by: Takafumi Arakaki <[email protected]>
(cherry picked from commit 32b1305)

Author: 2 people

test/threads.jl

@@ -4,6 +4,8 @@ using Test
 
 using Base.Threads
 
+include("print_process_affinity.jl") # import `uv_thread_getaffinity`
+
 # simple sanity tests for locks under cooperative concurrent access
 let lk = ReentrantLock()
     c1 = Event()
@@ -93,10 +95,13 @@ else
 end
 # Note also that libuv does not support affinity in macOS and it is known to
 # hang in FreeBSD. So, it's tested only in Linux and Windows:
-if Sys.islinux() || Sys.iswindows()
-    if Sys.CPU_THREADS > 1 && !running_under_rr()
-        @test run_with_affinity([2]) == "2"
-        @test run_with_affinity([1, 2]) == "1,2"
+const AFFINITY_SUPPORTED = (Sys.islinux() || Sys.iswindows()) && !running_under_rr()
+
+if AFFINITY_SUPPORTED
+    allowed_cpus = findall(uv_thread_getaffinity())
+    if length(allowed_cpus) ≥ 2
+        @test run_with_affinity(allowed_cpus[1:1]) == "$(allowed_cpus[1])"
+        @test run_with_affinity(allowed_cpus[1:2]) == "$(allowed_cpus[1]),$(allowed_cpus[2])"
     end
 end