#define MREMAP_FIXED 2
/*
- * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping.
+ * mremap wrapper for non-Linux systems not allowing MAYMOVE.
* This is not generic.
*/
static
void *mremap_wrapper(void *old_address, size_t old_size,
size_t new_size, int flags)
{
- void *new_address;
-
- assert(flags & MREMAP_MAYMOVE);
- assert(!(flags & MREMAP_FIXED));
- new_address = mmap(old_address, new_size,
- PROT_READ | PROT_WRITE,
- MAP_ANONYMOUS | MAP_PRIVATE,
- -1, 0);
- if (new_address == MAP_FAILED)
- return MAP_FAILED;
- if (old_address) {
- memcpy(new_address, old_address, old_size);
- munmap(old_address, old_size);
- }
- return new_address;
+ assert(!(flags & MREMAP_MAYMOVE));
+
+ return MAP_FAILED;
}
#endif
/* Sleep delay in us */
#define RCU_SLEEP_DELAY 1000
-#define ARENA_INIT_ALLOC 16
+#define INIT_NR_THREADS 8
+#define ARENA_INIT_ALLOC \
+ sizeof(struct registry_chunk) \
+ + INIT_NR_THREADS * sizeof(struct rcu_reader)
/*
* Active attempts to check for reader Q.S. before calling sleep().
static CDS_LIST_HEAD(registry);
+struct registry_chunk {
+ size_t data_len; /* data length */
+ size_t used; /* data used */
+ struct cds_list_head node; /* chunk_list node */
+ char data[];
+};
+
struct registry_arena {
- void *p;
- size_t len;
- size_t used;
+ struct cds_list_head chunk_list;
};
-static struct registry_arena registry_arena;
+static struct registry_arena registry_arena = {
+ .chunk_list = CDS_LIST_HEAD_INIT(registry_arena.chunk_list),
+};
/* Saved fork signal mask, protected by rcu_gp_lock */
static sigset_t saved_fork_signal_mask;
}
/*
- * only grow for now.
+ * Only grow for now. If empty, allocate a ARENA_INIT_ALLOC sized chunk.
+ * Else, try expanding the last chunk. If this fails, allocate a new
+ * chunk twice as big as the last chunk.
+ * Memory used by chunks _never_ moves. A chunk could theoretically be
+ * freed when all "used" slots are released, but we don't do it at this
+ * point.
*/
-static void resize_arena(struct registry_arena *arena, size_t len)
+static
+void expand_arena(struct registry_arena *arena)
{
- void *new_p;
- size_t old_len;
-
- old_len = arena->len;
-
- if (!arena->p)
- new_p = mmap(arena->p, len,
+ struct registry_chunk *new_chunk, *last_chunk;
+ size_t old_chunk_len, new_chunk_len;
+
+ /* No chunk. */
+ if (cds_list_empty(&arena->chunk_list)) {
+ assert(ARENA_INIT_ALLOC >=
+ sizeof(struct registry_chunk)
+ + sizeof(struct rcu_reader));
+ new_chunk_len = ARENA_INIT_ALLOC;
+ new_chunk = mmap(NULL, new_chunk_len,
PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE,
-1, 0);
- else
- new_p = mremap_wrapper(arena->p, old_len,
- len, MREMAP_MAYMOVE);
- assert(new_p != MAP_FAILED);
+ if (new_chunk == MAP_FAILED)
+ abort();
+ bzero(new_chunk, new_chunk_len);
+ new_chunk->data_len =
+ new_chunk_len - sizeof(struct registry_chunk);
+ cds_list_add_tail(&new_chunk->node, &arena->chunk_list);
+ return; /* We're done. */
+ }
- /*
- * Zero the newly allocated memory. Since mmap() does not
- * clearly specify if memory is zeroed or not (although it is
- * very likely that it is), be extra careful by not expecting
- * the new range to be zeroed by mremap.
- */
- bzero(new_p + old_len, len - old_len);
+ /* Try expanding last chunk. */
+ last_chunk = cds_list_entry(arena->chunk_list.prev,
+ struct registry_chunk, node);
+ old_chunk_len =
+ last_chunk->data_len + sizeof(struct registry_chunk);
+ new_chunk_len = old_chunk_len << 1;
+
+ /* Don't allow memory mapping to move, just expand. */
+ new_chunk = mremap_wrapper(last_chunk, old_chunk_len,
+ new_chunk_len, 0);
+ if (new_chunk != MAP_FAILED) {
+ /* Should not have moved. */
+ assert(new_chunk == last_chunk);
+ bzero((char *) last_chunk + old_chunk_len,
+ new_chunk_len - old_chunk_len);
+ last_chunk->data_len =
+ new_chunk_len - sizeof(struct registry_chunk);
+ return; /* We're done. */
+ }
- /*
- * If we did not re-use the same region, we need to update the
- * arena pointer.
- */
- if (new_p != arena->p)
- arena->p = new_p;
+ /* Remap did not succeed, we need to add a new chunk. */
+ new_chunk = mmap(NULL, new_chunk_len,
+ PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE,
+ -1, 0);
+ if (new_chunk == MAP_FAILED)
+ abort();
+ bzero(new_chunk, new_chunk_len);
+ new_chunk->data_len =
+ new_chunk_len - sizeof(struct registry_chunk);
+ cds_list_add_tail(&new_chunk->node, &arena->chunk_list);
+}
+
+static
+struct rcu_reader *arena_alloc(struct registry_arena *arena)
+{
+ struct registry_chunk *chunk;
+ struct rcu_reader *rcu_reader_reg;
+ int expand_done = 0; /* Only allow to expand once per alloc */
+ size_t len = sizeof(struct rcu_reader);
- arena->len = len;
+retry:
+ cds_list_for_each_entry(chunk, &arena->chunk_list, node) {
+ if (chunk->data_len - chunk->used < len)
+ continue;
+ /* Find spot */
+ for (rcu_reader_reg = (struct rcu_reader *) &chunk->data[0];
+ rcu_reader_reg < (struct rcu_reader *) &chunk->data[chunk->data_len];
+ rcu_reader_reg++) {
+ if (!rcu_reader_reg->alloc) {
+ rcu_reader_reg->alloc = 1;
+ chunk->used += len;
+ return rcu_reader_reg;
+ }
+ }
+ }
+
+ if (!expand_done) {
+ expand_arena(arena);
+ expand_done = 1;
+ goto retry;
+ }
+
+ return NULL;
}
/* Called with signals off and mutex locked */
-static void add_thread(void)
+static
+void add_thread(void)
{
struct rcu_reader *rcu_reader_reg;
- if (registry_arena.len
- < registry_arena.used + sizeof(struct rcu_reader))
- resize_arena(®istry_arena,
- caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC));
- /*
- * Find a free spot.
- */
- for (rcu_reader_reg = registry_arena.p;
- (void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
- rcu_reader_reg++) {
- if (!rcu_reader_reg->alloc)
- break;
- }
- rcu_reader_reg->alloc = 1;
- registry_arena.used += sizeof(struct rcu_reader);
+ rcu_reader_reg = arena_alloc(®istry_arena);
+ if (!rcu_reader_reg)
+ abort();
/* Add to registry */
rcu_reader_reg->tid = pthread_self();
assert(rcu_reader_reg->ctr == 0);
cds_list_add(&rcu_reader_reg->node, ®istry);
+ /*
+ * Reader threads are pointing to the reader registry. This is
+ * why its memory should never be relocated.
+ */
URCU_TLS(rcu_reader) = rcu_reader_reg;
}
/* Called with signals off and mutex locked */
static void rcu_gc_registry(void)
{
+ struct registry_chunk *chunk;
struct rcu_reader *rcu_reader_reg;
- pthread_t tid;
- int ret;
- for (rcu_reader_reg = registry_arena.p;
- (void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
- rcu_reader_reg++) {
- if (!rcu_reader_reg->alloc)
- continue;
- tid = rcu_reader_reg->tid;
- ret = pthread_kill(tid, 0);
- assert(ret != EINVAL);
- if (ret == ESRCH) {
- cds_list_del(&rcu_reader_reg->node);
- rcu_reader_reg->ctr = 0;
- rcu_reader_reg->alloc = 0;
- registry_arena.used -= sizeof(struct rcu_reader);
+ cds_list_for_each_entry(chunk, ®istry_arena.chunk_list, node) {
+ for (rcu_reader_reg = (struct rcu_reader *) &chunk->data[0];
+ rcu_reader_reg < (struct rcu_reader *) &chunk->data[chunk->data_len];
+ rcu_reader_reg++) {
+ pthread_t tid;
+ int ret;
+
+ if (!rcu_reader_reg->alloc)
+ continue;
+ tid = rcu_reader_reg->tid;
+ ret = pthread_kill(tid, 0);
+ assert(ret != EINVAL);
+ if (ret == ESRCH) {
+ cds_list_del(&rcu_reader_reg->node);
+ rcu_reader_reg->ctr = 0;
+ rcu_reader_reg->alloc = 0;
+ chunk->used -= sizeof(struct rcu_reader);
+ }
+
}
}
}
void rcu_bp_exit(void)
{
- if (registry_arena.p)
- munmap(registry_arena.p, registry_arena.len);
+ struct registry_chunk *chunk, *tmp;
+
+ cds_list_for_each_entry_safe(chunk, tmp,
+ ®istry_arena.chunk_list, node) {
+ munmap(chunk, chunk->data_len + sizeof(struct registry_chunk));
+ }
}
/*
projects / userspace-rcu.git / commitdiff
