remove restriction on number of threads running (#36778)

Closes #36469

src/threading.c

@@ -407,16 +407,13 @@ void jl_init_threading(void)
 #endif
 
  // how many threads available, usable
- int max_threads = jl_cpu_threads();
  jl_n_threads = JULIA_NUM_THREADS;
  if (jl_options.nthreads < 0) // --threads=auto
- jl_n_threads = max_threads;
+ jl_n_threads = jl_cpu_threads();
  else if (jl_options.nthreads > 0) // --threads=N
  jl_n_threads = jl_options.nthreads;
  else if ((cp = getenv(NUM_THREADS_NAME)))
  jl_n_threads = (uint64_t)strtol(cp, NULL, 10);
- if (jl_n_threads > max_threads)
- jl_n_threads = max_threads;
  if (jl_n_threads <= 0)
  jl_n_threads = 1;
 #ifndef __clang_analyzer__
@@ -451,6 +448,10 @@ void jl_start_threads(void)
  // according to a 'compact' policy
  // non-exclusive: no affinity settings; let the kernel move threads about
  if (exclusive) {
+ if (jl_n_threads > jl_cpu_threads()) {
+ jl_n_threads = 1;
+ jl_error("Too many threads running for " MACHINE_EXCLUSIVE_NAME " option.");
+ }
  memset(mask, 0, cpumasksize);
  mask[0] = 1;
  uvtid = (uv_thread_t)uv_thread_self();

test/cmdlineargs.jl

@@ -190,29 +190,31 @@ let exename = `$(Base.julia_cmd()) --startup-file=no`
 
  # -t, --threads
  code = "print(Threads.nthreads())"
- cpu_threads = ccall(:jl_cpu_threads, Int32, ())
- @test string(cpu_threads) ==
+ cpu_threads = string(ccall(:jl_cpu_threads, Int32, ()))
+ @test cpu_threads ==
  read(`$exename --threads auto -e $code`, String) ==
  read(`$exename --threads=auto -e $code`, String) ==
  read(`$exename -tauto -e $code`, String) ==
- read(`$exename -t auto -e $code`, String) ==
- read(`$exename -t $(cpu_threads+1) -e $code`, String)
- if cpu_threads > 1
- for nt in (nothing, "1"); withenv("JULIA_NUM_THREADS"=>nt) do
- @test read(`$exename --threads 2 -e $code`, String) ==
- read(`$exename --threads=2 -e $code`, String) ==
- read(`$exename -t2 -e $code`, String) ==
+ read(`$exename -t auto -e $code`, String)
+ for nt in (nothing, "1")
+ withenv("JULIA_NUM_THREADS" => nt) do
+ @test read(`$exename --threads=2 -e $code`, String) ==
  read(`$exename -t 2 -e $code`, String) == "2"
- end end
+ end
+ end
+ cpu_threads *= "0"
+ @test read(`$exename -t $cpu_threads -e $code`, String) == cpu_threads
+ withenv("JULIA_NUM_THREADS" => cpu_threads) do
+ @test read(`$exename -e $code`, String) == cpu_threads
  end
  @test !success(`$exename -t 0`)
  @test !success(`$exename -t -1`)
 
  # Combining --threads and --procs: --threads does propagate
- if cpu_threads > 1; withenv("JULIA_NUM_THREADS"=>nothing) do
+ withenv("JULIA_NUM_THREADS" => nothing) do
  code = "print(sum(remotecall_fetch(Threads.nthreads, x) for x in procs()))"
  @test read(`$exename -p2 -t2 -e $code`, String) == "6"
- end end
+ end
 
  # --procs
  @test readchomp(`$exename -q -p 2 -e "println(nworkers())"`) == "2"