*/
#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
#include <sys/mman.h>
#include "rculfhash-internal.h"
#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)