Use linked-list & spinlock to avoid non-safe functions. Closes #1102

* Most functions - including pthreads, malloc, free, etc are not safe to use in
  signal handlers. So we use a simple spin-lock and manual linked-list to manage
  our list of PIDs to wait on.

renderdoc/common/threading.h

@@ -55,9 +55,36 @@ public:
 private:
   RWLock *m_RW;
 };
+
+class SpinLock
+{
+public:
+  void Lock()
+  {
+    while(!Trylock())
+    {
+      // spin!
+    }
+  }
+  bool Trylock() { return Atomic::CmpExch32(&val, 0, 1) == 0; }
+  void Unlock() { Atomic::CmpExch32(&val, 1, 0); }
+private:
+  volatile int32_t val = 0;
+};
+
+class ScopedSpinLock
+{
+public:
+  ScopedSpinLock(SpinLock &spin) : m_Spin(&spin) { m_Spin->Lock(); }
+  ~ScopedSpinLock() { m_Spin->Unlock(); }
+private:
+  SpinLock *m_Spin;
+};
 };
 
 #define SCOPED_LOCK(cs) Threading::ScopedLock CONCAT(scopedlock, __LINE__)(cs);
 
 #define SCOPED_READLOCK(rw) Threading::ScopedReadLock CONCAT(scopedlock, __LINE__)(rw);
 #define SCOPED_WRITELOCK(rw) Threading::ScopedWriteLock CONCAT(scopedlock, __LINE__)(rw);
+
+#define SCOPED_SPINLOCK(cs) Threading::SpinLock CONCAT(scopedlock, __LINE__)(cs);

renderdoc/common/threading_tests.cpp

@@ -0,0 +1,74 @@
+/******************************************************************************
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Baldur Karlsson
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ ******************************************************************************/
+
+#include "common/threading.h"
+#include "os/os_specific.h"
+
+#if ENABLED(ENABLE_UNIT_TESTS)
+
+#include "3rdparty/catch/catch.hpp"
+
+static int value = 0;
+
+TEST_CASE("Test spin lock", "[threading]")
+{
+  int finalValue = 0;
+
+  std::vector<Threading::ThreadHandle> threads;
+  std::vector<int> threadcount;
+
+  threads.resize(8);
+  threadcount.resize(8);
+
+  Threading::SpinLock lock;
+
+  for(int i = 0; i < 8; i++)
+  {
+    threadcount[i] = (rand() & 0xff) << 4;
+
+    finalValue += threadcount[i];
+  }
+
+  for(int i = 0; i < 8; i++)
+  {
+    threads[i] = Threading::CreateThread([&lock, &threadcount, i]() {
+      for(int c = 0; c < threadcount[i]; c++)
+      {
+        lock.Lock();
+        value++;
+        lock.Unlock();
+      }
+    });
+  }
+
+  for(Threading::ThreadHandle t : threads)
+  {
+    Threading::JoinThread(t);
+    Threading::CloseThread(t);
+  }
+
+  CHECK(finalValue == value);
+}
+
+#endif    // ENABLED(ENABLE_UNIT_TESTS)