+// SPDX-FileCopyrightText: 2011 Lai Jiangshan <laijs@cn.fujitsu.com>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
/*
- * rculfhash-mm-mmap.c
- *
* mmap/reservation based memory management for Lock-Free RCU Hash Table
- *
- * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
#include <sys/mman.h>
+#include <urcu/assert.h>
#include "rculfhash-internal.h"
#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif
-/* reserve inaccessible memory space without allocation any memory */
-static void *memory_map(size_t length)
+/*
+ * The allocation scheme used by the mmap based RCU hash table is to make a
+ * large unaccessible mapping to reserve memory without allocating it.
+ * Then smaller chunks are allocated by overlapping read/write mappings which
+ * do allocate memory. Deallocation is done by an overlapping unaccessible
+ * mapping.
+ *
+ * This scheme was tested on Linux, macOS and Solaris. However, on Cygwin the
+ * mmap wrapper is based on the Windows NtMapViewOfSection API which doesn't
+ * support overlapping mappings.
+ *
+ * An alternative to the overlapping mappings is to use mprotect to change the
+ * protection on chunks of the large mapping, read/write to allocate and none
+ * to deallocate. This works perfecty on Cygwin and Solaris but on Linux a
+ * call to madvise is also required to deallocate and it just doesn't work on
+ * macOS.
+ *
+ * For this reason, we keep to original scheme on all platforms except Cygwin.
+ */
+
+
+/* Reserve inaccessible memory space without allocating it */
+static
+void *memory_map(size_t length)
{
- void *ret = mmap(NULL, length, PROT_NONE,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ void *ret;
- assert(ret != MAP_FAILED);
+ ret = mmap(NULL, length, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (ret == MAP_FAILED) {
+ perror("mmap");
+ abort();
+ }
return ret;
}
-static void memory_unmap(void *ptr, size_t length)
+static
+void memory_unmap(void *ptr, size_t length)
{
- int ret __attribute__((unused));
-
- ret = munmap(ptr, length);
+ if (munmap(ptr, length)) {
+ perror("munmap");
+ abort();
+ }
+}
- assert(ret == 0);
+#ifdef __CYGWIN__
+/* Set protection to read/write to allocate a memory chunk */
+static
+void memory_populate(void *ptr, size_t length)
+{
+ if (mprotect(ptr, length, PROT_READ | PROT_WRITE)) {
+ perror("mprotect");
+ abort();
+ }
}
-static void memory_populate(void *ptr, size_t length)
+/* Set protection to none to deallocate a memory chunk */
+static
+void memory_discard(void *ptr, size_t length)
{
- void *ret __attribute__((unused));
+ if (mprotect(ptr, length, PROT_NONE)) {
+ perror("mprotect");
+ abort();
+ }
+}
- ret = mmap(ptr, length, PROT_READ | PROT_WRITE,
- MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+#else /* __CYGWIN__ */
- assert(ret == ptr);
+static
+void memory_populate(void *ptr, size_t length)
+{
+ if (mmap(ptr, length, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0) != ptr) {
+ perror("mmap");
+ abort();
+ }
}
/*
* Discard garbage memory and avoid system save it when try to swap it out.
* Make it still reserved, inaccessible.
*/
-static void memory_discard(void *ptr, size_t length)
+static
+void memory_discard(void *ptr, size_t length)
{
- void *ret __attribute__((unused));
-
- ret = mmap(ptr, length, PROT_NONE,
- MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-
- assert(ret == ptr);
+ if (mmap(ptr, length, PROT_NONE,
+ MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0) != ptr) {
+ perror("mmap");
+ abort();
+ }
}
+#endif /* __CYGWIN__ */
static
void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
/* small table */
ht->tbl_mmap = calloc(ht->max_nr_buckets,
sizeof(*ht->tbl_mmap));
- assert(ht->tbl_mmap);
+ urcu_posix_assert(ht->tbl_mmap);
return;
}
/* large table */
/* large table */
unsigned long len = 1UL << (order - 1);
- assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
+ urcu_posix_assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
memory_populate(ht->tbl_mmap + len,
len * sizeof(*ht->tbl_mmap));
}
/* large table */
unsigned long len = 1UL << (order - 1);
- assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
+ urcu_posix_assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
memory_discard(ht->tbl_mmap + len, len * sizeof(*ht->tbl_mmap));
}
/* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */