https://bugs.gentoo.org/881161
https://github.com/rui314/mold/issues/410
https://github.com/oneapi-src/oneTBB/commit/ceacd2207edfb72a8fc235213265afe68ce74ad0
https://github.com/oneapi-src/oneTBB/commit/137c1a88b690acf3525e0f279720ac489ce66481

From ceacd2207edfb72a8fc235213265afe68ce74ad0 Mon Sep 17 00:00:00 2001
From: Ilya Isaev <ilya.isaev@intel.com>
Date: Wed, 26 Oct 2022 13:13:51 +0200
Subject: [PATCH] Rework test_eh_thread to avoid sporadic failures (#946)

Signed-off-by: Isaev, Ilya <ilya.isaev@intel.com>
--- a/test/tbb/test_eh_thread.cpp
+++ b/test/tbb/test_eh_thread.cpp
@@ -54,15 +54,16 @@ void limitThreads(size_t limit)
     CHECK_MESSAGE(0 == ret, "setrlimit has returned an error");
 }
 
-static bool g_exception_caught = false;
-static std::mutex m;
-static std::condition_variable cv;
-static std::atomic<bool> stop{ false };
+size_t getThreadLimit() {
+    rlimit rlim;
+
+    int ret = getrlimit(RLIMIT_NPROC, &rlim);
+    CHECK_MESSAGE(0 == ret, "getrlimit has returned an error");
+    return rlim.rlim_cur;
+}
 
 static void* thread_routine(void*)
 {
-    std::unique_lock<std::mutex> lock(m);
-    cv.wait(lock, [] { return stop == true; });
     return nullptr;
 }
 
@@ -94,32 +95,17 @@ TEST_CASE("Too many threads") {
     }
 
     // Some systems set really big limit (e.g. >45К) for the number of processes/threads
-    limitThreads(1024);
-
-    std::thread /* isolate test */ ([] {
-        std::vector<Thread> threads;
-        stop = false;
-        auto finalize = [&] {
-            stop = true;
-            cv.notify_all();
-            for (auto& t : threads) {
-                t.join();
-            }
-        };
-
-        for (int i = 0;; ++i) {
+    limitThreads(1);
+    if (getThreadLimit() == 1) {
+        for (int attempt = 0; attempt < 5; ++attempt) {
             Thread thread;
-            if (!thread.isValid()) {
-                break;
-            }
-            threads.push_back(thread);
-            if (i == 1024) {
-                WARN_MESSAGE(false, "setrlimit seems having no effect");
-                finalize();
+            if (thread.isValid()) {
+                WARN_MESSAGE(false, "We were able to create a thread. setrlimit seems having no effect");
+                thread.join();
                 return;
             }
         }
-        g_exception_caught = false;
+        bool g_exception_caught = false;
         try {
             // Initialize the library to create worker threads
             tbb::parallel_for(0, 2, [](int) {});
@@ -132,9 +118,10 @@ TEST_CASE("Too many threads") {
         }
         // Do not CHECK to avoid memory allocation (we can be out of memory)
         if (!g_exception_caught) {
-            FAIL("No exception was caught");
+            FAIL("No exception was thrown on library initialization");
         }
-        finalize();
-    }).join();
+    } else {
+        WARN_MESSAGE(false, "setrlimit seems having no effect");
+    }
 }
 #endif

From 137c1a88b690acf3525e0f279720ac489ce66481 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Wed, 26 Oct 2022 04:54:20 -0700
Subject: [PATCH] Retry if pthread_create fails with EAGAIN (#824)

Signed-off-by: Rui Ueyama <ruiu@cs.stanford.edu>
--- a/src/tbb/rml_thread_monitor.h
+++ b/src/tbb/rml_thread_monitor.h
@@ -31,6 +31,7 @@
 #include <pthread.h>
 #include <cstring>
 #include <cstdlib>
+#include <time.h>
 #else
 #error Unsupported platform
 #endif
@@ -191,8 +192,25 @@ inline thread_monitor::handle_type thread_monitor::launch( void* (*thread_routin
     check(pthread_attr_init( &s ), "pthread_attr_init has failed");
     if( stack_size>0 )
         check(pthread_attr_setstacksize( &s, stack_size ), "pthread_attr_setstack_size has failed" );
+
+    // pthread_create(2) can spuriously fail with EAGAIN. We retry
+    // max_num_tries times with progressively longer wait times.
     pthread_t handle;
-    check( pthread_create( &handle, &s, thread_routine, arg ), "pthread_create has failed" );
+    const int max_num_tries = 20;
+    int error = EAGAIN;
+
+    for (int i = 0; i < max_num_tries && error == EAGAIN; i++) {
+      if (i != 0) {
+        // Wait i milliseconds
+        struct timespec ts = {0, i * 1000 * 1000};
+        nanosleep(&ts, NULL);
+      }
+      error = pthread_create(&handle, &s, thread_routine, arg);
+    }
+
+    if (error)
+      handle_perror(error, "pthread_create has failed");
+
     check( pthread_attr_destroy( &s ), "pthread_attr_destroy has failed" );
     return handle;
 }