Import trimmed svn-1.8.0-rc3

1 files changed, 655 insertions, 0 deletions

diff --git a/subversion/libsvn_subr/named_atomic.c b/subversion/libsvn_subr/named_atomic.c
new file mode 100644
index 0000000..d07e742
--- /dev/null
+++ b/subversion/libsvn_subr/named_atomic.c
@@ -0,0 +1,655 @@
+/*
+ * svn_named_atomic.c: routines for machine-wide named atomics.
+ *
+ * ====================================================================
+ *    Licensed to the Apache Software Foundation (ASF) under one
+ *    or more contributor license agreements.  See the NOTICE file
+ *    distributed with this work for additional information
+ *    regarding copyright ownership.  The ASF licenses this file
+ *    to you under the Apache License, Version 2.0 (the
+ *    "License"); you may not use this file except in compliance
+ *    with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing,
+ *    software distributed under the License is distributed on an
+ *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *    KIND, either express or implied.  See the License for the
+ *    specific language governing permissions and limitations
+ *    under the License.
+ * ====================================================================
+ */
+
+#include "private/svn_named_atomic.h"
+
+#include <apr_global_mutex.h>
+#include <apr_mmap.h>
+
+#include "svn_private_config.h"
+#include "private/svn_atomic.h"
+#include "private/svn_mutex.h"
+#include "svn_pools.h"
+#include "svn_dirent_uri.h"
+#include "svn_io.h"
+
+/* Implementation aspects.
+ *
+ * We use a single shared memory block (memory mapped file) that will be
+ * created by the first user and merely mapped by all subsequent ones.
+ * The memory block contains an short header followed by a fixed-capacity
+ * array of named atomics. The number of entries currently in use is stored
+ * in the header part.
+ *
+ * Finding / creating the MMAP object as well as adding new array entries
+ * is being guarded by an APR global mutex. Since releasing the MMAP
+ * structure and closing the underlying does not affect other users of the
+ * same, cleanup will not be synchronized.
+ *
+ * The array is append-only.  Once a process mapped the block into its
+ * address space, it may freely access any of the used entries.  However,
+ * it must synchronize access to the volatile data within the entries.
+ * On Windows and where otherwise supported by GCC, lightweight "lock-free"
+ * synchronization will be used. Other targets serialize all access using
+ * a global mutex.
+ *
+ * Atomics will be identified by their name (a short string) and lookup
+ * takes linear time. But even that takes only about 10 microseconds for a
+ * full array scan -- which is in the same order of magnitude than e.g. a
+ * single global mutex lock / unlock pair.
+ */
+
+/* Capacity of our shared memory object, i.e. max number of named atomics
+ * that may be created. Should have the form 2**N - 1.
+ */
+#define MAX_ATOMIC_COUNT 1023
+
+/* We choose the size of a single named atomic object to fill a complete
+ * cache line (on most architectures).  Thereby, we minimize the cache
+ * sync. overhead between different CPU cores.
+ */
+#define CACHE_LINE_LENGTH 64
+
+/* We need 8 bytes for the actual value and the remainder is used to
+ * store the NUL-terminated name.
+ *
+ * Must not be smaller than SVN_NAMED_ATOMIC__MAX_NAME_LENGTH.
+ */
+#define MAX_NAME_LENGTH (CACHE_LINE_LENGTH - sizeof(apr_int64_t) - 1)
+
+/* Particle that will be appended to the namespace name to form the
+ * name of the mutex / lock file used for that namespace.
+ */
+#define MUTEX_NAME_SUFFIX ".mutex"
+
+/* Particle that will be appended to the namespace name to form the
+ * name of the shared memory file that backs that namespace.
+ */
+#define SHM_NAME_SUFFIX ".shm"
+
+/* Platform-dependent implementations of our basic atomic operations.
+ * NA_SYNCHRONIZE(op) will ensure that the OP gets executed atomically.
+ * This will be zero-overhead if OP itself is already atomic.
+ *
+ * (We don't call it SYNCHRONIZE because Windows has a preprocess macro by
+ * that name.)
+ *
+ * The default implementation will use the same mutex for initialization
+ * as well as any type of data access.  This is quite expensive and we
+ * can do much better on most platforms.
+ */
+#if defined(WIN32) && ((_WIN32_WINNT >= 0x0502) || defined(InterlockedExchangeAdd64))
+
+/* Interlocked API / intrinsics guarantee full data synchronization
+ */
+#define synched_read(mem) *mem
+#define synched_write(mem, value) InterlockedExchange64(mem, value)
+#define synched_add(mem, delta) InterlockedExchangeAdd64(mem, delta)
+#define synched_cmpxchg(mem, value, comperand) \
+  InterlockedCompareExchange64(mem, value, comperand)
+
+#define NA_SYNCHRONIZE(_atomic,op) op;
+#define NA_SYNCHRONIZE_IS_FAST TRUE
+
+#elif SVN_HAS_ATOMIC_BUILTINS
+
+/* GCC provides atomic intrinsics for most common CPU types
+ */
+#define synched_read(mem) *mem
+#define synched_write(mem, value) __sync_lock_test_and_set(mem, value)
+#define synched_add(mem, delta) __sync_add_and_fetch(mem, delta)
+#define synched_cmpxchg(mem, value, comperand) \
+  __sync_val_compare_and_swap(mem, comperand, value)
+
+#define NA_SYNCHRONIZE(_atomic,op) op;
+#define NA_SYNCHRONIZE_IS_FAST TRUE
+
+#else
+
+/* Default implementation
+ */
+static apr_int64_t
+synched_read(volatile apr_int64_t *mem)
+{
+  return *mem;
+}
+
+static apr_int64_t
+synched_write(volatile apr_int64_t *mem, apr_int64_t value)
+{
+  apr_int64_t old_value = *mem;
+  *mem = value;
+
+  return old_value;
+}
+
+static apr_int64_t
+synched_add(volatile apr_int64_t *mem, apr_int64_t delta)
+{
+  return *mem += delta;
+}
+
+static apr_int64_t
+synched_cmpxchg(volatile apr_int64_t *mem,
+                apr_int64_t value,
+                apr_int64_t comperand)
+{
+  apr_int64_t old_value = *mem;
+  if (old_value == comperand)
+    *mem = value;
+
+  return old_value;
+}
+
+#define NA_SYNCHRONIZE(_atomic,op)\
+  do{\
+  SVN_ERR(lock(_atomic->mutex));\
+  op;\
+  SVN_ERR(unlock(_atomic->mutex,SVN_NO_ERROR));\
+  }while(0)
+
+#define NA_SYNCHRONIZE_IS_FAST FALSE
+
+#endif
+
+/* Structure describing a single atomic: its VALUE and NAME.
+ */
+struct named_atomic_data_t
+{
+  volatile apr_int64_t value;
+  char name[MAX_NAME_LENGTH + 1];
+};
+
+/* Content of our shared memory buffer.  COUNT is the number
+ * of used entries in ATOMICS.  Insertion is append-only.
+ * PADDING is used to align the header information with the
+ * atomics to create a favorable data alignment.
+ */
+struct shared_data_t
+{
+  volatile apr_uint32_t count;
+  char padding [sizeof(struct named_atomic_data_t) - sizeof(apr_uint32_t)];
+
+  struct named_atomic_data_t atomics[MAX_ATOMIC_COUNT];
+};
+
+/* Structure combining all objects that we need for access serialization.
+ */
+struct mutex_t
+{
+  /* Inter-process sync. is handled by through lock file. */
+  apr_file_t *lock_file;
+
+  /* Pool to be used with lock / unlock functions */
+  apr_pool_t *pool;
+};
+
+/* API structure combining the atomic data and the access mutex
+ */
+struct svn_named_atomic__t
+{
+  /* pointer into the shared memory */
+  struct named_atomic_data_t *data;
+
+  /* sync. object; never NULL (even if unused) */
+  struct mutex_t *mutex;
+};
+
+/* This is intended to be a singleton struct.  It contains all
+ * information necessary to initialize and access the shared
+ * memory.
+ */
+struct svn_atomic_namespace__t
+{
+  /* Pointer to the shared data mapped into our process */
+  struct shared_data_t *data;
+
+  /* Last time we checked, this was the number of used
+   * (i.e. fully initialized) items.  I.e. we can read
+   * their names without further sync. */
+  volatile svn_atomic_t min_used;
+
+  /* for each atomic in the shared memory, we hand out
+   * at most one API-level object. */
+  struct svn_named_atomic__t atomics[MAX_ATOMIC_COUNT];
+
+  /* Synchronization object for this namespace */
+  struct mutex_t mutex;
+};
+
+/* On most operating systems APR implements file locks per process, not
+ * per file. I.e. the lock file will only sync. among processes but within
+ * a process, we must use a mutex to sync the threads. */
+/* Compare ../libsvn_fs_fs/fs.h:SVN_FS_FS__USE_LOCK_MUTEX */
+#if APR_HAS_THREADS && !defined(WIN32)
+#define USE_THREAD_MUTEX 1
+#else
+#define USE_THREAD_MUTEX 0
+#endif
+
+/* Used for process-local thread sync.
+ */
+static svn_mutex__t *thread_mutex = NULL;
+
+/* Initialization flag for the above used by svn_atomic__init_once.
+ */
+static volatile svn_atomic_t mutex_initialized = FALSE;
+
+/* Initialize the thread sync. structures.
+ * To be called by svn_atomic__init_once.
+ */
+static svn_error_t *
+init_thread_mutex(void *baton, apr_pool_t *pool)
+{
+  /* let the mutex live as long as the APR */
+  apr_pool_t *global_pool = svn_pool_create(NULL);
+
+  return svn_mutex__init(&thread_mutex, USE_THREAD_MUTEX, global_pool);
+}
+
+/* Utility that acquires our global mutex and converts error types.
+ */
+static svn_error_t *
+lock(struct mutex_t *mutex)
+{
+  svn_error_t *err;
+
+  /* Get lock on the filehandle. */
+  SVN_ERR(svn_mutex__lock(thread_mutex));
+  err = svn_io_lock_open_file(mutex->lock_file, TRUE, FALSE, mutex->pool);
+
+  return err
+    ? svn_mutex__unlock(thread_mutex, err)
+    : err;
+}
+
+/* Utility that releases the lock previously acquired via lock().  If the
+ * unlock succeeds and OUTER_ERR is not NULL, OUTER_ERR will be returned.
+ * Otherwise, return the result of the unlock operation.
+ */
+static svn_error_t *
+unlock(struct mutex_t *mutex, svn_error_t * outer_err)
+{
+  svn_error_t *unlock_err
+      = svn_io_unlock_open_file(mutex->lock_file, mutex->pool);
+  return svn_mutex__unlock(thread_mutex,
+                           svn_error_compose_create(outer_err,
+                                                    unlock_err));
+}
+
+/* The last user to close a particular namespace should also remove the
+ * lock file.  Failure to do so, however, does not affect further uses
+ * of the same namespace.
+ */
+static apr_status_t
+delete_lock_file(void *arg)
+{
+  struct mutex_t *mutex = arg;
+  const char *lock_name = NULL;
+
+  /* locks have already been cleaned up. Simply close the file */
+  apr_status_t status = apr_file_close(mutex->lock_file);
+
+  /* Remove the file from disk. This will fail if there ares still other
+   * users of this lock file, i.e. namespace. */
+  apr_file_name_get(&lock_name, mutex->lock_file);
+  if (lock_name)
+    apr_file_remove(lock_name, mutex->pool);
+
+  return status;
+}
+
+/* Validate the ATOMIC parameter, i.e it's address.  Correct code will
+ * never need this but if someone should accidentally to use a NULL or
+ * incomplete structure, let's catch that here instead of segfaulting.
+ */
+static svn_error_t *
+validate(svn_named_atomic__t *atomic)
+{
+  return atomic && atomic->data && atomic->mutex
+    ? SVN_NO_ERROR
+    : svn_error_create(SVN_ERR_BAD_ATOMIC, 0, _("Not a valid atomic"));
+}
+
+/* Auto-initialize and return in *ATOMIC the API-level object for the
+ * atomic with index I within NS. */
+static void
+return_atomic(svn_named_atomic__t **atomic,
+              svn_atomic_namespace__t *ns,
+              int i)
+{
+  *atomic = &ns->atomics[i];
+  if (ns->atomics[i].data == NULL)
+    {
+      (*atomic)->mutex = &ns->mutex;
+      (*atomic)->data = &ns->data->atomics[i];
+    }
+}
+
+/* Implement API */
+
+svn_boolean_t
+svn_named_atomic__is_supported(void)
+{
+#ifdef _WIN32
+  static svn_tristate_t result = svn_tristate_unknown;
+
+  if (result == svn_tristate_unknown)
+    {
+      /* APR SHM implementation requires the creation of global objects */
+      HANDLE handle = CreateFileMappingA(INVALID_HANDLE_VALUE,
+                                         NULL,
+                                         PAGE_READONLY,
+                                         0,
+                                         1,
+                                         "Global\\__RandomXZY_svn");
+      if (handle != NULL)
+        {
+          CloseHandle(handle);
+          result = svn_tristate_true;
+        }
+      else
+        result = svn_tristate_false;
+    }
+
+  return result == svn_tristate_true;
+#else
+  return TRUE;
+#endif
+}
+
+svn_boolean_t
+svn_named_atomic__is_efficient(void)
+{
+  return NA_SYNCHRONIZE_IS_FAST;
+}
+
+svn_error_t *
+svn_atomic_namespace__create(svn_atomic_namespace__t **ns,
+                             const char *name,
+                             apr_pool_t *result_pool)
+{
+  apr_status_t apr_err;
+  svn_error_t *err;
+  apr_file_t *file;
+  apr_mmap_t *mmap;
+  const char *shm_name, *lock_name;
+  apr_finfo_t finfo;
+
+  apr_pool_t *subpool = svn_pool_create(result_pool);
+
+  /* allocate the namespace data structure
+   */
+  svn_atomic_namespace__t *new_ns = apr_pcalloc(result_pool, sizeof(**ns));
+
+  /* construct the names of the system objects that we need
+   */
+  shm_name = apr_pstrcat(subpool, name, SHM_NAME_SUFFIX, NULL);
+  lock_name = apr_pstrcat(subpool, name, MUTEX_NAME_SUFFIX, NULL);
+
+  /* initialize the lock objects
+   */
+  SVN_ERR(svn_atomic__init_once(&mutex_initialized, init_thread_mutex, NULL,
+                                result_pool));
+
+  new_ns->mutex.pool = result_pool;
+  SVN_ERR(svn_io_file_open(&new_ns->mutex.lock_file, lock_name,
+                           APR_READ | APR_WRITE | APR_CREATE,
+                           APR_OS_DEFAULT,
+                           result_pool));
+
+  /* Make sure the last user of our lock file will actually remove it.
+   * Please note that only the last file handle begin closed will actually
+   * remove the underlying file (see docstring for apr_file_remove).
+   */
+  apr_pool_cleanup_register(result_pool, &new_ns->mutex,
+                            delete_lock_file,
+                            apr_pool_cleanup_null);
+
+  /* Prevent concurrent initialization.
+   */
+  SVN_ERR(lock(&new_ns->mutex));
+
+  /* First, make sure that the underlying file exists.  If it doesn't
+   * exist, create one and initialize its content.
+   */
+  err = svn_io_file_open(&file, shm_name,
+                          APR_READ | APR_WRITE | APR_CREATE,
+                          APR_OS_DEFAULT,
+                          result_pool);
+  if (!err)
+    {
+      err = svn_io_stat(&finfo, shm_name, APR_FINFO_SIZE, subpool);
+      if (!err && finfo.size < sizeof(struct shared_data_t))
+        {
+           /* Zero all counters, values and names.
+            */
+           struct shared_data_t initial_data;
+           memset(&initial_data, 0, sizeof(initial_data));
+           err = svn_io_file_write_full(file, &initial_data,
+                                        sizeof(initial_data), NULL,
+                                        subpool);
+        }
+    }
+
+  /* Now, map it into memory.
+   */
+  if (!err)
+    {
+      apr_err = apr_mmap_create(&mmap, file, 0, sizeof(*new_ns->data),
+                                APR_MMAP_READ | APR_MMAP_WRITE , result_pool);
+      if (!apr_err)
+        new_ns->data = mmap->mm;
+      else
+        err = svn_error_createf(apr_err, NULL,
+                                _("MMAP failed for file '%s'"), shm_name);
+    }
+
+  svn_pool_destroy(subpool);
+
+  if (!err && new_ns->data)
+    {
+      /* Detect severe cases of corruption (i.e. when some outsider messed
+       * with our data file)
+       */
+      if (new_ns->data->count > MAX_ATOMIC_COUNT)
+        return svn_error_create(SVN_ERR_CORRUPTED_ATOMIC_STORAGE, 0,
+                       _("Number of atomics in namespace is too large."));
+
+      /* Cache the number of existing, complete entries.  There can't be
+       * incomplete ones from other processes because we hold the mutex.
+       * Our process will also not access this information since we are
+       * either being called from within svn_atomic__init_once or by
+       * svn_atomic_namespace__create for a new object.
+       */
+      new_ns->min_used = new_ns->data->count;
+      *ns = new_ns;
+    }
+
+  /* Unlock to allow other processes may access the shared memory as well.
+   */
+  return unlock(&new_ns->mutex, err);
+}
+
+svn_error_t *
+svn_atomic_namespace__cleanup(const char *name,
+                              apr_pool_t *pool)
+{
+  const char *shm_name, *lock_name;
+
+  /* file names used for the specified namespace */
+  shm_name = apr_pstrcat(pool, name, SHM_NAME_SUFFIX, NULL);
+  lock_name = apr_pstrcat(pool, name, MUTEX_NAME_SUFFIX, NULL);
+
+  /* remove these files if they exist */
+  SVN_ERR(svn_io_remove_file2(shm_name, TRUE, pool));
+  SVN_ERR(svn_io_remove_file2(lock_name, TRUE, pool));
+
+  return SVN_NO_ERROR;
+}
+
+svn_error_t *
+svn_named_atomic__get(svn_named_atomic__t **atomic,
+                      svn_atomic_namespace__t *ns,
+                      const char *name,
+                      svn_boolean_t auto_create)
+{
+  apr_uint32_t i, count;
+  svn_error_t *error = SVN_NO_ERROR;
+  apr_size_t len = strlen(name);
+
+  /* Check parameters and make sure we return a NULL atomic
+   * in case of failure.
+   */
+  *atomic = NULL;
+  if (len > SVN_NAMED_ATOMIC__MAX_NAME_LENGTH)
+    return svn_error_create(SVN_ERR_BAD_ATOMIC, 0,
+                            _("Atomic's name is too long."));
+
+  /* If no namespace has been provided, bail out.
+   */
+  if (ns == NULL || ns->data == NULL)
+    return svn_error_create(SVN_ERR_BAD_ATOMIC, 0,
+                            _("Namespace has not been initialized."));
+
+  /* Optimistic lookup.
+   * Because we never change the name of existing atomics and may only
+   * append new ones, we can safely compare the name of existing ones
+   * with the name that we are looking for.
+   */
+  for (i = 0, count = svn_atomic_read(&ns->min_used); i < count; ++i)
+    if (strncmp(ns->data->atomics[i].name, name, len + 1) == 0)
+      {
+        return_atomic(atomic, ns, i);
+        return SVN_NO_ERROR;
+      }
+
+  /* Try harder:
+   * Serialize all lookup and insert the item, if necessary and allowed.
+   */
+  SVN_ERR(lock(&ns->mutex));
+
+  /* We only need to check for new entries.
+   */
+  for (i = count; i < ns->data->count; ++i)
+    if (strncmp(ns->data->atomics[i].name, name, len + 1) == 0)
+      {
+        return_atomic(atomic, ns, i);
+
+        /* Update our cached number of complete entries. */
+        svn_atomic_set(&ns->min_used, ns->data->count);
+
+        return unlock(&ns->mutex, error);
+      }
+
+  /* Not found.  Append a new entry, if allowed & possible.
+   */
+  if (auto_create)
+    {
+      if (ns->data->count < MAX_ATOMIC_COUNT)
+        {
+          ns->data->atomics[ns->data->count].value = 0;
+          memcpy(ns->data->atomics[ns->data->count].name,
+                 name,
+                 len+1);
+
+          return_atomic(atomic, ns, ns->data->count);
+          ++ns->data->count;
+        }
+        else
+          error = svn_error_create(SVN_ERR_BAD_ATOMIC, 0,
+                                  _("Out of slots for named atomic."));
+    }
+
+  /* We are mainly done here.  Let others continue their work.
+   */
+  SVN_ERR(unlock(&ns->mutex, error));
+
+  /* Only now can we be sure that a full memory barrier has been set
+   * and that the new entry has been written to memory in full.
+   */
+  svn_atomic_set(&ns->min_used, ns->data->count);
+
+  return SVN_NO_ERROR;
+}
+
+svn_error_t *
+svn_named_atomic__read(apr_int64_t *value,
+                       svn_named_atomic__t *atomic)
+{
+  SVN_ERR(validate(atomic));
+  NA_SYNCHRONIZE(atomic, *value = synched_read(&atomic->data->value));
+
+  return SVN_NO_ERROR;
+}
+
+svn_error_t *
+svn_named_atomic__write(apr_int64_t *old_value,
+                        apr_int64_t new_value,
+                        svn_named_atomic__t *atomic)
+{
+  apr_int64_t temp;
+
+  SVN_ERR(validate(atomic));
+  NA_SYNCHRONIZE(atomic, temp = synched_write(&atomic->data->value, new_value));
+
+  if (old_value)
+    *old_value = temp;
+
+  return SVN_NO_ERROR;
+}
+
+svn_error_t *
+svn_named_atomic__add(apr_int64_t *new_value,
+                      apr_int64_t delta,
+                      svn_named_atomic__t *atomic)
+{
+  apr_int64_t temp;
+
+  SVN_ERR(validate(atomic));
+  NA_SYNCHRONIZE(atomic, temp = synched_add(&atomic->data->value, delta));
+
+  if (new_value)
+    *new_value = temp;
+
+  return SVN_NO_ERROR;
+}
+
+svn_error_t *
+svn_named_atomic__cmpxchg(apr_int64_t *old_value,
+                          apr_int64_t new_value,
+                          apr_int64_t comperand,
+                          svn_named_atomic__t *atomic)
+{
+  apr_int64_t temp;
+
+  SVN_ERR(validate(atomic));
+  NA_SYNCHRONIZE(atomic, temp = synched_cmpxchg(&atomic->data->value,
+                                                new_value,
+                                                comperand));
+
+  if (old_value)
+    *old_value = temp;
+
+  return SVN_NO_ERROR;
+}