Rework, reduce the size, add proper locking

 -Erik

1 files changed, 329 insertions, 32 deletions

diff --git a/libc/stdlib/malloc-930716/malloc.c b/libc/stdlib/malloc-930716/malloc.c
index 88c9251ad..f4c147f0c 100644
--- a/libc/stdlib/malloc-930716/malloc.c
+++ b/libc/stdlib/malloc-930716/malloc.c
@@ -8,42 +8,69 @@
    WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY OF THIS
    SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. */
 
+#define _GNU_SOURCE
+#include <features.h>
 #include <limits.h>
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include "malloc.h"
 
+#define MIN(x,y) ({ \
+	const typeof(x) _x = (x);       \
+	const typeof(y) _y = (y);       \
+	(void) (&_x == &_y);            \
+	_x < _y ? _x : _y; })
+
+
+#ifdef __UCLIBC_HAS_THREADS__
+#include <pthread.h>
+static pthread_mutex_t malloclock = PTHREAD_MUTEX_INITIALIZER;
+# define LOCK	pthread_mutex_lock(&malloclock)
+# define UNLOCK	pthread_mutex_unlock(&malloclock);
+#else
+# define LOCK
+# define UNLOCK
+#endif
+    
+static void * malloc_unlocked (size_t size);
+static void free_unlocked(void *ptr);
+static void * __default_morecore_init(long size);
+
 /* How to really get more memory. */
-void *(*__morecore)(long) = __default_morecore_init;
+static void *(*__morecore)(long) = __default_morecore_init;
 
 /* Pointer to the base of the first block. */
-char *_heapbase;
+static char *_heapbase;
 
 /* Block information table. */
-union info *_heapinfo;
+static union info *_heapinfo;
 
 /* Number of info entries. */
-static int heapsize;
+static size_t heapsize;
 
 /* Search index in the info table. */
-int _heapindex;
+static size_t _heapindex;
 
 /* Limit of valid info table indices. */
-int _heaplimit;
+static size_t _heaplimit;
 
 /* Count of large blocks allocated for each fragment size. */
-int _fragblocks[BLOCKLOG];
+static size_t _fragblocks[BLOCKLOG];
 
 /* Free lists for each fragment size. */
-struct list _fraghead[BLOCKLOG];
+static struct list _fraghead[BLOCKLOG];
 
 /* Are we experienced? */
 static int initialized;
 
-/* Aligned allocation. */
-static void *
-align(size_t size)
+
+
+/* Aligned allocation.
+ * Called within the lock in initialize() and morecore(), 
+ * so no explicit locking needed... */
+static void * align(size_t size)
 {
     void *result;
     unsigned int adj;
@@ -57,14 +84,16 @@ align(size_t size)
     return result;
 }
 
-/* Set everything up and remember that we have. */
-static int
-initialize(void)
+/* Set everything up and remember that we have. 
+ * Called within the lock in malloc(), so no
+ * explicit locking needed... */
+static int initialize(void)
 {
     heapsize = HEAP / BLOCKSIZE;
     _heapinfo = align(heapsize * sizeof (union info));
-    if (!_heapinfo)
+    if (!_heapinfo) {
 	return 0;
+    }
     memset(_heapinfo, 0, heapsize * sizeof (union info));
     _heapinfo[0].free.size = 0;
     _heapinfo[0].free.next = _heapinfo[0].free.prev = 0;
@@ -74,14 +103,15 @@ initialize(void)
     return 1;
 }
 
-/* Get neatly aligned memory, initializing or growing the
-   heap info table as necessary. */
-static void *
-morecore(size_t size)
+/* Get neatly aligned memory, initializing or growing the 
+ * heap info table as necessary. 
+ * Called within a lock in malloc() and free(), 
+ * so no explicit locking needed... */
+static void * morecore(size_t size)
 {
     void *result;
     union info *newinfo, *oldinfo;
-    int newsize;
+    size_t newsize;
 
     result = align(size);
     if (!result)
@@ -104,11 +134,7 @@ morecore(size_t size)
 	newinfo[BLOCK(oldinfo)].busy.info.size
 	    = BLOCKIFY(heapsize * sizeof (union info));
 	_heapinfo = newinfo;
-#if 0
-	free(oldinfo);
-#else
-	_free_internal (oldinfo);
-#endif
+	free_unlocked(oldinfo);
 	heapsize = newsize;
     }
 
@@ -116,16 +142,42 @@ morecore(size_t size)
     return result;
 }
 
+/* Note that morecore has to take a signed argument so
+   that negative values can return memory to the system. */
+static void * __default_morecore_init(long size)
+{
+    void *result;
+
+    result = sbrk(size);
+    if (result == (void *) -1)
+	return NULL;
+    return result;
+}
+
 /* Allocate memory from the heap. */
-void *
-malloc (size_t size)
+void * malloc (size_t size)
+{
+    void * ptr;
+    LOCK;
+    ptr = malloc_unlocked(size);
+    UNLOCK;
+    return(ptr);
+}
+
+static void * malloc_unlocked (size_t size)
 {
     void *result;
-    int log, block, blocks, i, lastblocks, start;
+    size_t log, block, blocks, i, lastblocks, start;
     struct list *next;
 
-    if (!initialized && !initialize())
+#if 1
+    /* Some programs will call malloc (0).  Lets be strict and return NULL */
+    if (size == 0)
 	return NULL;
+#endif
+
+    if (size < sizeof (struct list))
+	size = sizeof (struct list);
 
 #if 1
     /* Some programs will call malloc (0).  Lets be strict and return NULL */
@@ -136,6 +188,10 @@ malloc (size_t size)
     if (size < sizeof (struct list))
 	size = sizeof (struct list);
 
+    if (!initialized && !initialize()) {
+	return NULL;
+    }
+
     /* Determine the allocation policy based on the request size. */
     if (size <= BLOCKSIZE / 2) {
 	/* Small allocation to receive a fragment of a block. Determine
@@ -162,9 +218,10 @@ malloc (size_t size)
 	} else {
 	    /* No free fragments of the desired size, so get a new block
 	       and break it into fragments, returning the first. */
-	    result = malloc(BLOCKSIZE);
-	    if (!result)
+	    result = malloc_unlocked(BLOCKSIZE);
+	    if (!result) {
 		return NULL;
+	    }
 	    ++_fragblocks[log];
 
 	    /* Link all fragments but the first into the free list. */
@@ -213,8 +270,9 @@ malloc (size_t size)
 		    continue;
 		}
 		result = morecore(blocks * BLOCKSIZE);
-		if (!result)
+		if (!result) {
 		    return NULL;
+		}
 		block = BLOCK(result);
 		_heapinfo[block].busy.type = 0;
 		_heapinfo[block].busy.info.size = blocks;
@@ -252,3 +310,242 @@ malloc (size_t size)
 
     return result;
 }
+
+
+
+/* Return memory to the heap. */
+void free(void *ptr)
+{
+    LOCK;
+    free_unlocked(ptr);
+    UNLOCK;
+}
+
+static void free_unlocked(void *ptr)
+{
+    int block, blocks, i, type;
+    struct list *prev, *next;
+
+    if (ptr == NULL)
+	return;
+
+    block = BLOCK(ptr);
+
+    switch (type = _heapinfo[block].busy.type) {
+	case 0:
+	    /* Find the free cluster previous to this one in the free list.
+	       Start searching at the last block referenced; this may benefit
+	       programs with locality of allocation. */
+	    i = _heapindex;
+	    if (i > block)
+		while (i > block)
+		    i = _heapinfo[i].free.prev;
+	    else {
+		do
+		    i = _heapinfo[i].free.next;
+		while (i > 0 && i < block);
+		i = _heapinfo[i].free.prev;
+	    }
+
+	    /* Determine how to link this block into the free list. */
+	    if (block == i + _heapinfo[i].free.size) {
+		/* Coalesce this block with its predecessor. */
+		_heapinfo[i].free.size += _heapinfo[block].busy.info.size;
+		block = i;
+	    } else {
+		/* Really link this block back into the free list. */
+		_heapinfo[block].free.size = _heapinfo[block].busy.info.size;
+		_heapinfo[block].free.next = _heapinfo[i].free.next;
+		_heapinfo[block].free.prev = i;
+		_heapinfo[i].free.next = block;
+		_heapinfo[_heapinfo[block].free.next].free.prev = block;
+	    }
+
+	    /* Now that the block is linked in, see if we can coalesce it
+	       with its successor (by deleting its successor from the list
+	       and adding in its size). */
+	    if (block + _heapinfo[block].free.size == _heapinfo[block].free.next) {
+		_heapinfo[block].free.size
+		    += _heapinfo[_heapinfo[block].free.next].free.size;
+		_heapinfo[block].free.next
+		    = _heapinfo[_heapinfo[block].free.next].free.next;
+		_heapinfo[_heapinfo[block].free.next].free.prev = block;
+	    }
+
+	    /* Now see if we can return stuff to the system. */
+	    blocks = _heapinfo[block].free.size;
+	    if (blocks >= FINAL_FREE_BLOCKS && block + blocks == _heaplimit
+		    && (*__morecore)(0) == ADDRESS(block + blocks)) {
+		_heaplimit -= blocks;
+		(*__morecore)(-blocks * BLOCKSIZE);
+		_heapinfo[_heapinfo[block].free.prev].free.next
+		    = _heapinfo[block].free.next;
+		_heapinfo[_heapinfo[block].free.next].free.prev
+		    = _heapinfo[block].free.prev;
+		block = _heapinfo[block].free.prev;
+	    }
+
+	    /* Set the next search to begin at this block. */
+	    _heapindex = block;
+	    break;
+
+	default:
+	    /* Get the address of the first free fragment in this block. */
+	    prev = (struct list *) ((char *) ADDRESS(block)
+		    + (_heapinfo[block].busy.info.frag.first
+			<< type));
+
+	    if (_heapinfo[block].busy.info.frag.nfree == (BLOCKSIZE >> type) - 1
+		    && _fragblocks[type] > 1) {
+		/* If all fragments of this block are free, remove them
+		   from the fragment list and free the whole block. */
+		--_fragblocks[type];
+		for (next = prev, i = 1; i < BLOCKSIZE >> type; ++i)
+		    next = next->next;
+		prev->prev->next = next;
+		if (next)
+		    next->prev = prev->prev;
+		_heapinfo[block].busy.type = 0;
+		_heapinfo[block].busy.info.size = 1;
+		free_unlocked(ADDRESS(block));
+	    } else if (_heapinfo[block].busy.info.frag.nfree) {
+		/* If some fragments of this block are free, link this fragment
+		   into the fragment list after the first free fragment of
+		   this block. */
+		next = ptr;
+		next->next = prev->next;
+		next->prev = prev;
+		prev->next = next;
+		if (next->next)
+		    next->next->prev = next;
+		++_heapinfo[block].busy.info.frag.nfree;
+	    } else {
+		/* No fragments of this block are free, so link this fragment
+		   into the fragment list and announce that it is the first
+		   free fragment of this block. */
+		prev = (struct list *) ptr;
+		_heapinfo[block].busy.info.frag.nfree = 1;
+		_heapinfo[block].busy.info.frag.first
+		    = (unsigned int) ((char *) ptr - (char *) NULL) % BLOCKSIZE
+		    >> type;
+		prev->next = _fraghead[type].next;
+		prev->prev = &_fraghead[type];
+		prev->prev->next = prev;
+		if (prev->next)
+		    prev->next->prev = prev;
+	    }
+	    break;
+    }
+}
+
+/* Resize the given region to the new size, returning a pointer
+   to the (possibly moved) region.  This is optimized for speed;
+   some benchmarks seem to indicate that greater compactness is
+   achieved by unconditionally allocating and copying to a
+   new region. */
+void * realloc (void *ptr, size_t size)
+{
+    void *result, *previous;
+    size_t block, blocks, type;
+    size_t oldlimit;
+
+    if (!ptr)
+	return malloc(size);
+    if (!size) {
+	LOCK;
+	free_unlocked(ptr);
+	result = malloc_unlocked(0);
+	UNLOCK;
+	return(result);
+    }
+
+    LOCK;
+    block = BLOCK(ptr);
+
+    switch (type = _heapinfo[block].busy.type) {
+	case 0:
+	    /* Maybe reallocate a large block to a small fragment. */
+	    if (size <= BLOCKSIZE / 2) {
+		if ((result = malloc_unlocked(size)) != NULL) {
+		    memcpy(result, ptr, size);
+		    free(ptr);
+		}
+		UNLOCK;
+		return result;
+	    }
+
+	    /* The new size is a large allocation as well; see if
+	       we can hold it in place. */
+	    blocks = BLOCKIFY(size);
+	    if (blocks < _heapinfo[block].busy.info.size) {
+		/* The new size is smaller; return excess memory
+		   to the free list. */
+		_heapinfo[block + blocks].busy.type = 0;
+		_heapinfo[block + blocks].busy.info.size
+		    = _heapinfo[block].busy.info.size - blocks;
+		_heapinfo[block].busy.info.size = blocks;
+		free(ADDRESS(block + blocks));
+		UNLOCK;
+		return ptr;
+	    } else if (blocks == _heapinfo[block].busy.info.size) {
+		/* No size change necessary. */
+		UNLOCK;
+		return ptr;
+	    } else {
+		/* Won't fit, so allocate a new region that will.  Free
+		   the old region first in case there is sufficient adjacent
+		   free space to grow without moving. */
+		blocks = _heapinfo[block].busy.info.size;
+		/* Prevent free from actually returning memory to the system. */
+		oldlimit = _heaplimit;
+		_heaplimit = 0;
+		free(ptr);
+		_heaplimit = oldlimit;
+		result = malloc_unlocked(size);
+		if (!result) {
+		    /* Now we're really in trouble.  We have to unfree
+		       the thing we just freed.  Unfortunately it might
+		       have been coalesced with its neighbors. */
+		    if (_heapindex == block)
+			malloc_unlocked(blocks * BLOCKSIZE);
+		    else {
+			previous = malloc_unlocked((block - _heapindex) * BLOCKSIZE);
+			malloc_unlocked(blocks * BLOCKSIZE);
+			free(previous);
+		    }	    
+		    UNLOCK;
+		    return NULL;
+		}
+		if (ptr != result)
+		    memmove(result, ptr, blocks * BLOCKSIZE);
+		UNLOCK;
+		return result;
+	    }
+	    break;
+
+	default:
+	    /* Old size is a fragment; type is logarithm to base two of
+	       the fragment size. */
+	    if ((size > 1 << (type - 1)) && (size <= 1 << type)) {
+		/* New size is the same kind of fragment. */
+		UNLOCK;
+		return ptr;
+	    }
+	    else {
+		/* New size is different; allocate a new space, and copy
+		   the lesser of the new size and the old. */
+		result = malloc_unlocked(size);
+		if (!result) {
+		    UNLOCK;
+		    return NULL;
+		}
+		memcpy(result, ptr, MIN(size, (size_t)(1 << type)));
+		free(ptr);
+		UNLOCK;
+		return result;
+	    }
+	    break;
+    }
+    UNLOCK;
+}
+