Move file locking into the RTS, fixing #629, #1109

File locking (of the Haskell 98 variety) was previously done using a
static table with linear search, which had two problems: the array had
a fixed size and was sometimes too small (#1109), and performance of
lockFile/unlockFile was suboptimal due to the linear search.
Also the algorithm failed to count readers as required by Haskell 98
(#629).

Now it's done using a hash table (provided by the RTS).  Furthermore I
avoided the extra fstat() for every open file by passing the dev_t and
ino_t into lockFile.  This and the improvements to the locking
algorithm result in a healthy 20% or so performance increase for
opening/closing files (see openFile008 test).

1 files changed, 11 insertions, 0 deletions

diff --git a/rts/RtsStartup.c b/rts/RtsStartup.c
index cdb45c60f2..4f84468b0a 100644
--- a/rts/RtsStartup.c
+++ b/rts/RtsStartup.c
@@ -33,6 +33,7 @@
 #include "RtsTypeable.h"
 #include "Stable.h"
 #include "Hpc.h"
+#include "FileLock.h"
 
 #if defined(RTS_GTK_FRONTPANEL)
 #include "FrontPanel.h"
@@ -238,6 +239,11 @@ hs_init(int *argc, char **argv[])
     /* initialise the shared Typeable store */
     initTypeableStore();
 
+    /* initialise file locking, if necessary */
+#if !defined(mingw32_HOST_OS)    
+    initFileLocking();
+#endif
+
 #if defined(DEBUG)
     /* initialise thread label table (tso->char*) */
     initThreadLabelTable();
@@ -462,6 +468,11 @@ hs_exit_(rtsBool wait_foreign)
     /* free shared Typeable store */
     exitTypeableStore();
 
+    /* free file locking tables, if necessary */
+#if !defined(mingw32_HOST_OS)    
+    freeFileLocking();
+#endif
+
     /* free the stable pointer table */
     exitStablePtrTable();