wfcqueue: combine C++ API cds_wfcq_head_cast with overloading

[urcu.git] / src / rculfhash-mm-mmap.c

diff --git a/src/rculfhash-mm-mmap.c b/src/rculfhash-mm-mmap.c
index 3cc3fa01c9d5ed5c16888ae8f02fb85ae65cf1de..4bce972094881bf3d8dc031be87241cd933b18c4 100644 (file)
--- a/src/rculfhash-mm-mmap.c
+++ b/src/rculfhash-mm-mmap.c
@@ -21,55 +21,110 @@
  */
 
 #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)
@@ -79,7 +134,7 @@ 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 */
@@ -91,7 +146,7 @@ void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
                /* 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));
        }
@@ -119,7 +174,7 @@ void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
                /* 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 */