Better control of the IO manager thread; improvements to deadlock checking

    
In the threaded RTS on *nix platforms:
    
 - we now start the IO manager thread eagerly at startup time
   (previously was started on demand).

 - we now ask the IO manager thread to stop at shutdown
    
 - In Timer.c:handle_tick, if it looks like we might be in a
   deadlock, instead of calling prodOneCapability() which was known to be
   wrong, we now send a byte down the IO manager's pipe to wake it up.
  
This also avoids a case of double-acquisition of a mutex, which
happened if prodOneCapability() was called while the current thread
was holding a mutex.

2 files changed, 43 insertions, 1 deletions

diff --git a/rts/posix/Signals.c b/rts/posix/Signals.c
index 5f5f77fd39..2303d9f89b 100644
--- a/rts/posix/Signals.c
+++ b/rts/posix/Signals.c
@@ -16,6 +16,7 @@
 #include "posix/Signals.h"
 #include "RtsUtils.h"
 #include "RtsFlags.h"
+#include "Prelude.h"
 
 #ifdef alpha_HOST_ARCH
 # if defined(linux_HOST_OS)
@@ -107,6 +108,9 @@ more_handlers(I_ sig)
 // Here's the pipe into which we will send our signals
 static int io_manager_pipe = -1;
 
+#define IO_MANAGER_WAKEUP 0xff
+#define IO_MANAGER_DIE    0xfe
+
 void
 setIOManagerPipe (int fd)
 {
@@ -115,6 +119,40 @@ setIOManagerPipe (int fd)
     io_manager_pipe = fd;
 }
 
+#if defined(THREADED_RTS)
+void
+ioManagerWakeup (void)
+{
+    // Wake up the IO Manager thread by sending a byte down its pipe
+    if (io_manager_pipe >= 0) {
+	StgWord8 byte = (StgWord8)IO_MANAGER_WAKEUP;
+	write(io_manager_pipe, &byte, 1);
+    }
+}
+
+void
+ioManagerDie (void)
+{
+    // Ask the IO Manager thread to exit
+    if (io_manager_pipe >= 0) {
+	StgWord8 byte = (StgWord8)IO_MANAGER_DIE;
+	write(io_manager_pipe, &byte, 1);
+    }
+}
+
+void
+ioManagerStart (void)
+{
+    // Make sure the IO manager thread is running
+    Capability *cap;
+    if (io_manager_pipe < 0) {
+	cap = rts_lock();
+	rts_evalIO(cap,&GHCziConc_ensureIOManagerIsRunning_closure,NULL);
+	rts_unlock(cap);
+    }
+}
+#endif
+
 #if !defined(THREADED_RTS)
 
 #define N_PENDING_HANDLERS 16
diff --git a/rts/posix/Signals.h b/rts/posix/Signals.h
index 39477f8c6a..b005abb5b5 100644
--- a/rts/posix/Signals.h
+++ b/rts/posix/Signals.h
@@ -12,12 +12,16 @@
 extern rtsBool anyUserHandlers(void);
 
 #if !defined(THREADED_RTS)
-
 extern StgPtr pending_handler_buf[];
 extern StgPtr *next_pending_handler;
 #define signals_pending() (next_pending_handler != pending_handler_buf)
 void startSignalHandlers(Capability *cap);
+#endif
 
+#if defined(THREADED_RTS)
+void ioManagerWakeup (void);
+void ioManagerDie (void);
+void ioManagerStart (void);
 #endif
 
 extern StgInt *signal_handlers;