Kernel: Move block condition evaluation out of the Scheduler

This makes the Scheduler a lot leaner by not having to evaluate
block conditions every time it is invoked. Instead evaluate them as
the states change, and unblock threads at that point.

This also implements some more waitid/waitpid/wait features and
behavior. For example, WUNTRACED and WNOWAIT are now supported. And
wait will now not return EINTR when SIGCHLD is delivered at the
same time.

1 files changed, 8 insertions, 0 deletions

diff --git a/Kernel/DoubleBuffer.h b/Kernel/DoubleBuffer.h
index b855fb8853..6db3718b8e 100644
--- a/Kernel/DoubleBuffer.h
+++ b/Kernel/DoubleBuffer.h
@@ -29,6 +29,7 @@
 #include <AK/Types.h>
 #include <Kernel/KBuffer.h>
 #include <Kernel/Lock.h>
+#include <Kernel/Thread.h>
 #include <Kernel/UserOrKernelBuffer.h>
 
 namespace Kernel {
@@ -53,6 +54,12 @@ public:
 
     size_t space_for_writing() const { return m_space_for_writing; }
 
+    void set_unblock_callback(Function<void()> callback)
+    {
+        ASSERT(!m_unblock_callback);
+        m_unblock_callback = move(callback);
+    }
+
 private:
     void flip();
     void compute_lockfree_metadata();
@@ -68,6 +75,7 @@ private:
     InnerBuffer m_buffer2;
 
     KBuffer m_storage;
+    Function<void()> m_unblock_callback;
     size_t m_capacity { 0 };
     size_t m_read_buffer_index { 0 };
     size_t m_space_for_writing { 0 };