From d175d3a8425c48ce4739f167b9a6eb80d3678685 Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Wed, 13 Jun 2012 17:26:41 +0000
Subject: More work in progress. The problem with release of the elements of a
 fileSystemList by one routine while some other (caller) routine is still
 traversing that list is not dependent on threaded operations.  An unthreaded
 build can still encounter the problem.  Revised so that threaded/unthreaded
 operations are much closer to the same (no direct TCL_THREADS dependency). 
 Also simplified the epoch checking which reduces locking to when it's needed.
  Still have the problem of returning as valid FilesystemRecords that are
 pulled from an outdated epoch.

---
 generic/tclIOUtil.c | 45 +++++++--------------------------------------
 1 file changed, 7 insertions(+), 38 deletions(-)

diff --git a/generic/tclIOUtil.c b/generic/tclIOUtil.c
index f8141ee..d98e760 100644
--- a/generic/tclIOUtil.c
+++ b/generic/tclIOUtil.c
@@ -39,16 +39,11 @@ static void		FsAddMountsToGlobResult(Tcl_Obj *resultPtr,
 			    Tcl_GlobTypeData *types);
 static void		FsUpdateCwd(Tcl_Obj *cwdObj, ClientData clientData);
 
-#ifdef TCL_THREADS
 static void		FsRecacheFilesystemList(void);
 static void		Purge(FilesystemRecord *fsRecPtr);
 
 #define Claim() (tsdPtr->claims++)
 #define Disclaim() if (--tsdPtr->claims <= 0) Purge(tsdPtr->filesystemList);
-#else
-#define Claim() 
-#define Disclaim()
-#endif
 
 /*
  * These form part of the native filesystem support. They are needed here
@@ -590,7 +585,6 @@ TclFSCwdPointerEquals(
     }
 }
 
-#ifdef TCL_THREADS
 static void
 FsRecacheFilesystemList(void)
 {
@@ -614,12 +608,10 @@ FsRecacheFilesystemList(void)
     }
 
     /*
-     * Code below operates on shared data. We are already called under mutex
-     * lock so we can safely proceed.
-     *
      * Locate tail of the global filesystem list.
      */
 
+    Tcl_MutexLock(&filesystemMutex);
     fsRecPtr = filesystemList;
     while (fsRecPtr != NULL) {
 	tmpFsRecPtr = fsRecPtr;
@@ -639,6 +631,8 @@ FsRecacheFilesystemList(void)
 	tsdPtr->filesystemList = tmpFsRecPtr;
 	fsRecPtr = fsRecPtr->prevPtr;
     }
+    tsdPtr->filesystemEpoch = theFilesystemEpoch;
+    Tcl_MutexUnlock(&filesystemMutex);
 
     /*
      * Make sure the above gets released on thread exit.
@@ -649,27 +643,16 @@ FsRecacheFilesystemList(void)
 	tsdPtr->initialized = 1;
     }
 }
-#endif /* TCL_THREADS */
 
 static FilesystemRecord *
 FsGetFirstFilesystem(void)
 {
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-    FilesystemRecord *fsRecPtr;
-#ifndef TCL_THREADS
-    tsdPtr->filesystemEpoch = theFilesystemEpoch;
-    fsRecPtr = filesystemList;
-#else
-    Tcl_MutexLock(&filesystemMutex);
     if (tsdPtr->filesystemList == NULL
 	    || (tsdPtr->filesystemEpoch != theFilesystemEpoch)) {
 	FsRecacheFilesystemList();
-	tsdPtr->filesystemEpoch = theFilesystemEpoch;
     }
-    Tcl_MutexUnlock(&filesystemMutex);
-    fsRecPtr = tsdPtr->filesystemList;
-#endif
-    return fsRecPtr;
+    return tsdPtr->filesystemList;
 }
 
 /*
@@ -681,12 +664,9 @@ int
 TclFSEpochOk(
     int filesystemEpoch)
 {
-    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-    (void) FsGetFirstFilesystem();
-    return (filesystemEpoch == tsdPtr->filesystemEpoch);
+    return (filesystemEpoch == theFilesystemEpoch);
 }
 
-#ifdef TCL_THREADS
 static void
 Purge(
     FilesystemRecord *fsRecPtr)
@@ -712,7 +692,6 @@ Purge(
 	toRelease = fsRecPtr;
     }
 }
-#endif
 
 /*
  * If non-NULL, clientData is owned by us and must be freed later.
@@ -832,6 +811,7 @@ TclFinalizeFilesystem(void)
 	}
 	fsRecPtr = tmpFsRecPtr;
     }
+    theFilesystemEpoch++;
     filesystemList = NULL;
 
     /*
@@ -869,6 +849,7 @@ void
 TclResetFilesystem(void)
 {
     filesystemList = &nativeFilesystemRecord;
+    theFilesystemEpoch++;
 
     /*
      * Note, at this point, I believe nativeFilesystemRecord -> fileRefCount
@@ -1451,9 +1432,7 @@ TclFSNormalizeToUniquePath(
 				 * for a given filesystem, we can optionally
 				 * return an fs-specific clientdata here. */
 {
-#ifdef TCL_THREADS
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-#endif
     FilesystemRecord *fsRecPtr, *firstFsRecPtr;
     /* Ignore this variable */
     (void) clientDataPtr;
@@ -3686,9 +3665,7 @@ Tcl_FSLink(
 Tcl_Obj*
 Tcl_FSListVolumes(void)
 {
-#ifdef TCL_THREADS
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-#endif
     FilesystemRecord *fsRecPtr;
     Tcl_Obj *resultPtr = Tcl_NewObj();
 
@@ -3743,9 +3720,7 @@ FsListMounts(
     Tcl_Obj *pathPtr,		/* Contains path to directory to search. */
     const char *pattern)	/* Pattern to match against. */
 {
-#ifdef TCL_THREADS
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-#endif
     FilesystemRecord *fsRecPtr;
     Tcl_GlobTypeData mountsOnly = { TCL_GLOB_TYPE_MOUNT, 0, NULL, NULL };
     Tcl_Obj *resultPtr = NULL;
@@ -3892,9 +3867,7 @@ TclFSInternalToNormalized(
     ClientData clientData,
     FilesystemRecord **fsRecPtrPtr)
 {
-#ifdef TCL_THREADS
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-#endif
     FilesystemRecord *fsRecPtr = FsGetFirstFilesystem();
 
     Claim();
@@ -4012,9 +3985,7 @@ TclFSNonnativePathType(
 				 * path, already with a refCount for the
 				 * caller. */
 {
-#ifdef TCL_THREADS
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-#endif
     FilesystemRecord *fsRecPtr;
     Tcl_PathType type = TCL_PATH_RELATIVE;
 
@@ -4475,9 +4446,7 @@ Tcl_Filesystem *
 Tcl_FSGetFileSystemForPath(
     Tcl_Obj* pathPtr)
 {
-#ifdef TCL_THREADS
     ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&tclFsDataKey);
-#endif
     FilesystemRecord *fsRecPtr;
     Tcl_Filesystem* retVal = NULL;
 
-- 
cgit v0.12