Implemented fork() support. We basically need to re-get the heap area

after fork()ing and recreate all semaphores we've been using. To do
the latter, we simply maintain a list of all locks.
fork()ing multithreaded teams can still be troublesome.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@12097 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kernel/libroot/posix/malloc/arch-specific.cpp

@@ -23,6 +23,7 @@
 #include <OS.h>
 #include <Debug.h>
 
+#include <stdlib.h>
 #include <unistd.h>
 
 using namespace BPrivate;
@@ -33,17 +34,43 @@ struct free_chunk {
 	size_t		size;
 };
 
+typedef DoublyLinkedList<hoardLockType> LockList;
+
+
 static const size_t kInitialHeapSize = 50 * B_PAGE_SIZE;
 	// that's about what hoard allocates anyway
 
 static area_id sHeapArea;
 static hoardLockType sHeapLock;
-static addr_t sHeapBase;
-static size_t sHeapSize, sHeapAreaSize;
+static void *sHeapBase;
+static addr_t sFreeHeapBase;
+static size_t sFreeHeapSize, sHeapAreaSize;
 static free_chunk *sFreeChunks;
+static LockList sLockList;
+
+static void initialize_hoard_lock(hoardLockType &lock, const char *name);
+static void reinitialize_hoard_lock(hoardLockType &lock);
 
 
-// ToDo: add real fork() support!
+static void
+init_after_fork()
+{
+	// re-initialize all locks
+	for (LockList::Iterator it = sLockList.GetIterator(); it.HasNext();) {
+		hoardLockType *lock = it.Next();
+		reinitialize_hoard_lock(*lock);
+	}
+
+	// find the heap area
+	sHeapArea = area_for(sHeapBase);
+	if (sHeapArea < 0) {
+		// Where is it gone?
+		debug_printf("hoard: init_after_fork(): thread %ld, Heap area not "
+			"found! Base address: %p\n", find_thread(NULL), sHeapBase);
+		exit(1);
+	}
+}
+
 
 extern "C" status_t
 __init_heap(void)
@@ -54,16 +81,62 @@ __init_heap(void)
 	// ToDo: add a VM call that instructs other areas to avoid the space after the heap when possible
 	//	(and if not, create it at the end of that range, so that the heap can grow as much as possible)
 	//	Then, move the heap back to 256 or 512 MB
-	sHeapBase = 0x30000000;
+	sHeapBase = (void*)0x30000000;
 		// let the heap start at 3*256 MB for now
 
 	sHeapArea = create_area("heap", (void **)&sHeapBase, B_BASE_ADDRESS,
 		sHeapAreaSize, B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
+	sFreeHeapBase = (addr_t)sHeapBase;
+
+	// init the lock list, and the heap lock
+	// Thereafter all locks should be initialized with hoardLockInit(). They
+	// will be properly re-initialized after a fork(). Note, that also the
+	// heap lock is initialized with hoardLockInit() -- this works fine
+	// and has the advantage, that it is in the lock list itself and we won't
+	// need any special handling on fork().
+	new (&sLockList) LockList;
 
 	hoardLockInit(sHeapLock, "heap");
-	return sHeapArea >= B_OK ? B_OK : sHeapArea;
+
+	if (sHeapArea < 0)
+		return sHeapArea;
+
+	atfork(&init_after_fork);
+		// Note: Needs malloc(). Hence we need to be fully initialized.
+		// ToDo: We should actually also install a hook that is called before
+		// fork() is being executed. In a multithreaded app it would need to
+		// acquire *all* allocator locks, so that we don't fork() an
+		// inconsistent state.
+
+	return B_OK;
 }
 
+
+static void
+initialize_hoard_lock(hoardLockType &lock, const char *name)
+{
+	lock.ben = 0;
+	lock.sem = create_sem(0, name);
+	if (lock.sem < 0) {
+		debug_printf("hoard: initialize_hoard_lock(): Failed to create "
+			"semaphore");
+	}
+}
+
+
+static void
+reinitialize_hoard_lock(hoardLockType &lock)
+{
+	// Get an info for the original semaphore, so we can name it just the same.
+	// This can fail e.g. in case the original team is already gone.
+	sem_info info;
+	if (get_sem_info(lock.sem, &info) == B_OK)
+		initialize_hoard_lock(lock, info.name);
+	else
+		initialize_hoard_lock(lock, "reinitialized hoard lock");
+}
+
+
 namespace BPrivate {
 
 void *
@@ -77,7 +150,6 @@ hoardSbrk(long size)
 	hoardLock(sHeapLock);
 
 	// find chunk in free list
-	
 	free_chunk *chunk = sFreeChunks, *last = NULL;
 	for (; chunk != NULL; chunk = chunk->next, last = chunk) {
 		if (chunk->size < (size_t)size)
@@ -101,22 +173,23 @@ hoardSbrk(long size)
 			sFreeChunks = chunk;
 
 		hoardUnlock(sHeapLock);
+
 		return address;
 	}
 
 	// There was no chunk, let's see if the area is large enough
 
-	size_t oldHeapSize = sHeapSize;
-	sHeapSize += size;
+	size_t oldHeapSize = sFreeHeapSize;
+	sFreeHeapSize += size;
 
 	// round to next page size
-	size_t pageSize = (sHeapSize + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);
+	size_t pageSize = (sFreeHeapSize + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);
 
 	if (pageSize < sHeapAreaSize) {
 		SERIAL_PRINT(("HEAP-%ld: heap area large enough for %ld\n", find_thread(NULL), size));
 		// the area is large enough already
 		hoardUnlock(sHeapLock);
-		return (void *)(sHeapBase + oldHeapSize);
+		return (void *)(sFreeHeapBase + oldHeapSize);
 	}
 
 	// We need to grow the area
@@ -133,7 +206,8 @@ hoardSbrk(long size)
 	sHeapAreaSize = pageSize;
 
 	hoardUnlock(sHeapLock);
-	return (void *)(sHeapBase + oldHeapSize);
+
+	return (void *)(sFreeHeapBase + oldHeapSize);
 }
 
 
@@ -147,8 +221,15 @@ hoardUnsbrk(void *ptr, long size)
 void
 hoardLockInit(hoardLockType &lock, const char *name)
 {
-	lock.ben = 0;
-	lock.sem = create_sem(0, name);
+	new (&lock) hoardLockType;
+		// init's the list link
+
+	initialize_hoard_lock(lock, name);
+
+	// add the lock to the lock list (the heap lock also protects the lock list)
+	hoardLock(sHeapLock);
+	sLockList.Add(&lock);
+	hoardUnlock(sHeapLock);
 }
 
 

src/kernel/libroot/posix/malloc/arch-specific.h

@@ -22,20 +22,21 @@
 
 #include "config.h"
 
+#include <new.h>
+
 #include <OS.h>
 #include <assert.h>
 
+#include <util/DoublyLinkedList.h>
 
-typedef struct {
+
+// Note: Since we're currently locks are never uninitialized, a singly linked
+// list would suffice. But we may change that some day, and the singly linked
+// list interface is ugly, anyway. ;-)
+struct hoardLockType : DoublyLinkedListLinkImpl<hoardLockType> {
 	int32	ben;
 	sem_id	sem;
-} hoardLockType;
-
-inline void *
-operator new(size_t, void *_P)
-{
-	return _P;
-}
+};
 
 namespace BPrivate {