#include "access/xlog.h"
#include "catalog/namespace.h"
#include "commands/async.h"
+#include "executor/execParallel.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "libpq/pqmq.h"
#define PARALLEL_KEY_TRANSACTION_SNAPSHOT UINT64CONST(0xFFFFFFFFFFFF0006)
#define PARALLEL_KEY_ACTIVE_SNAPSHOT UINT64CONST(0xFFFFFFFFFFFF0007)
#define PARALLEL_KEY_TRANSACTION_STATE UINT64CONST(0xFFFFFFFFFFFF0008)
-#define PARALLEL_KEY_EXTENSION_TRAMPOLINE UINT64CONST(0xFFFFFFFFFFFF0009)
+#define PARALLEL_KEY_ENTRYPOINT UINT64CONST(0xFFFFFFFFFFFF0009)
/* Fixed-size parallel state. */
typedef struct FixedParallelState
pid_t parallel_master_pid;
BackendId parallel_master_backend_id;
- /* Entrypoint for parallel workers. */
+ /* Entrypoint for parallel workers (deprecated)! */
parallel_worker_main_type entrypoint;
/* Mutex protects remaining fields. */
/* List of active parallel contexts. */
static dlist_head pcxt_list = DLIST_STATIC_INIT(pcxt_list);
+/*
+ * List of internal parallel worker entry points. We need this for
+ * reasons explained in LookupParallelWorkerFunction(), below.
+ */
+static const struct
+{
+ const char *fn_name;
+ parallel_worker_main_type fn_addr;
+} InternalParallelWorkers[] =
+
+{
+ {
+ "ParallelQueryMain", ParallelQueryMain
+ }
+};
+
/* Private functions. */
static void HandleParallelMessage(ParallelContext *pcxt, int i, StringInfo msg);
-static void ParallelExtensionTrampoline(dsm_segment *seg, shm_toc *toc);
static void WaitForParallelWorkersToExit(ParallelContext *pcxt);
+static parallel_worker_main_type LookupParallelWorkerFunction(char *libraryname, char *funcname);
/*
* Establish a new parallel context. This should be done after entering
* parallel mode, and (unless there is an error) the context should be
* destroyed before exiting the current subtransaction.
+ *
+ * NB: specifying the entrypoint as a function address is unportable.
+ * This will go away in Postgres 10, in favor of the API provided by
+ * CreateParallelContextForExternalFunction; in the meantime use that.
*/
ParallelContext *
CreateParallelContext(parallel_worker_main_type entrypoint, int nworkers)
}
/*
- * Establish a new parallel context that calls a function provided by an
- * extension. This works around the fact that the library might get mapped
- * at a different address in each backend.
+ * Establish a new parallel context that calls a function specified by name.
+ * Unlike CreateParallelContext, this is robust against possible differences
+ * in address space layout between different processes.
*/
ParallelContext *
CreateParallelContextForExternalFunction(char *library_name,
oldcontext = MemoryContextSwitchTo(TopTransactionContext);
/* Create the context. */
- pcxt = CreateParallelContext(ParallelExtensionTrampoline, nworkers);
+ pcxt = CreateParallelContext(NULL, nworkers);
pcxt->library_name = pstrdup(library_name);
pcxt->function_name = pstrdup(function_name);
pcxt->nworkers));
shm_toc_estimate_keys(&pcxt->estimator, 1);
- /* Estimate how much we'll need for extension entrypoint info. */
+ /* Estimate how much we'll need for entrypoint info. */
if (pcxt->library_name != NULL)
{
- Assert(pcxt->entrypoint == ParallelExtensionTrampoline);
Assert(pcxt->function_name != NULL);
shm_toc_estimate_chunk(&pcxt->estimator, strlen(pcxt->library_name)
+ strlen(pcxt->function_name) + 2);
}
shm_toc_insert(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, error_queue_space);
- /* Serialize extension entrypoint information. */
+ /* Serialize entrypoint information. */
if (pcxt->library_name != NULL)
{
Size lnamelen = strlen(pcxt->library_name);
+ strlen(pcxt->function_name) + 2);
strcpy(extensionstate, pcxt->library_name);
strcpy(extensionstate + lnamelen + 1, pcxt->function_name);
- shm_toc_insert(pcxt->toc, PARALLEL_KEY_EXTENSION_TRAMPOLINE,
+ shm_toc_insert(pcxt->toc, PARALLEL_KEY_ENTRYPOINT,
extensionstate);
}
}
}
/* Free memory. */
+ if (pcxt->library_name)
+ pfree(pcxt->library_name);
+ if (pcxt->function_name)
+ pfree(pcxt->function_name);
pfree(pcxt);
}
shm_mq *mq;
shm_mq_handle *mqh;
char *libraryspace;
+ char *entrypointstate;
+ parallel_worker_main_type entrypt;
char *gucspace;
char *combocidspace;
char *tsnapspace;
Assert(libraryspace != NULL);
RestoreLibraryState(libraryspace);
+ /*
+ * Identify the entry point to be called. In theory this could result in
+ * loading an additional library, though most likely the entry point is in
+ * the core backend or in a library we just loaded.
+ */
+ entrypointstate = shm_toc_lookup(toc, PARALLEL_KEY_ENTRYPOINT);
+ if (entrypointstate != NULL)
+ {
+ char *library_name;
+ char *function_name;
+
+ library_name = entrypointstate;
+ function_name = entrypointstate + strlen(library_name) + 1;
+
+ entrypt = LookupParallelWorkerFunction(library_name, function_name);
+ }
+ else
+ entrypt = fps->entrypoint;
+
/* Restore database connection. */
BackgroundWorkerInitializeConnectionByOid(fps->database_id,
fps->authenticated_user_id);
/*
* Time to do the real work: invoke the caller-supplied code.
*
- * If you get a crash at this line, see the comments for
- * ParallelExtensionTrampoline.
+ * If you get a crash at this line, try using
+ * CreateParallelContextForExternalFunction instead of
+ * CreateParallelContext.
*/
- fps->entrypoint(seg, toc);
+ entrypt(seg, toc);
/* Must exit parallel mode to pop active snapshot. */
ExitParallelMode();
pq_putmessage('X', NULL, 0);
}
-/*
- * It's unsafe for the entrypoint invoked by ParallelWorkerMain to be a
- * function living in a dynamically loaded module, because the module might
- * not be loaded in every process, or might be loaded but not at the same
- * address. To work around that problem, CreateParallelContextForExtension()
- * arranges to call this function rather than calling the extension-provided
- * function directly; and this function then looks up the real entrypoint and
- * calls it.
- */
-static void
-ParallelExtensionTrampoline(dsm_segment *seg, shm_toc *toc)
-{
- char *extensionstate;
- char *library_name;
- char *function_name;
- parallel_worker_main_type entrypt;
-
- extensionstate = shm_toc_lookup(toc, PARALLEL_KEY_EXTENSION_TRAMPOLINE);
- Assert(extensionstate != NULL);
- library_name = extensionstate;
- function_name = extensionstate + strlen(library_name) + 1;
-
- entrypt = (parallel_worker_main_type)
- load_external_function(library_name, function_name, true, NULL);
- entrypt(seg, toc);
-}
-
/*
* Update shared memory with the ending location of the last WAL record we
* wrote, if it's greater than the value already stored there.
fps->last_xlog_end = last_xlog_end;
SpinLockRelease(&fps->mutex);
}
+
+/*
+ * Look up (and possibly load) a parallel worker entry point function.
+ *
+ * For functions contained in the core code, we use library name "postgres"
+ * and consult the InternalParallelWorkers array. External functions are
+ * looked up, and loaded if necessary, using load_external_function().
+ *
+ * The point of this is to pass function names as strings across process
+ * boundaries. We can't pass actual function addresses because of the
+ * possibility that the function has been loaded at a different address
+ * in a different process. This is obviously a hazard for functions in
+ * loadable libraries, but it can happen even for functions in the core code
+ * on platforms using EXEC_BACKEND (e.g., Windows).
+ *
+ * At some point it might be worthwhile to get rid of InternalParallelWorkers[]
+ * in favor of applying load_external_function() for core functions too;
+ * but that raises portability issues that are not worth addressing now.
+ */
+static parallel_worker_main_type
+LookupParallelWorkerFunction(char *libraryname, char *funcname)
+{
+ /*
+ * If the function is to be loaded from postgres itself, search the
+ * InternalParallelWorkers array.
+ */
+ if (strcmp(libraryname, "postgres") == 0)
+ {
+ int i;
+
+ for (i = 0; i < lengthof(InternalParallelWorkers); i++)
+ {
+ if (strcmp(InternalParallelWorkers[i].fn_name, funcname) == 0)
+ return InternalParallelWorkers[i].fn_addr;
+ }
+
+ /* We can only reach this by programming error. */
+ elog(ERROR, "internal function \"%s\" not found", funcname);
+ }
+
+ /* Otherwise load from external library. */
+ return (parallel_worker_main_type)
+ load_external_function(libraryname, funcname, true, NULL);
+}
static BackgroundWorkerArray *BackgroundWorkerData;
/*
- * List of internal background workers. These are used for mapping the
- * function name to actual function when building with EXEC_BACKEND and also
- * to allow these to be loaded outside of shared_preload_libraries.
+ * List of internal background worker entry points. We need this for
+ * reasons explained in LookupBackgroundWorkerFunction(), below.
*/
-typedef struct InternalBGWorkerMain
+static const struct
{
- char *bgw_function_name;
- bgworker_main_type bgw_main;
-} InternalBGWorkerMain;
-
-static const InternalBGWorkerMain InternalBGWorkers[] = {
- {"ParallelWorkerMain", ParallelWorkerMain},
- /* Dummy entry marking end of the array. */
- {NULL, NULL}
+ const char *fn_name;
+ bgworker_main_type fn_addr;
+} InternalBGWorkers[] =
+
+{
+ {
+ "ParallelWorkerMain", ParallelWorkerMain
+ }
};
-static bgworker_main_type GetInternalBgWorkerMain(BackgroundWorker *worker);
+/* Private functions. */
+static bgworker_main_type LookupBackgroundWorkerFunction(char *libraryname, char *funcname);
+
/*
* Calculate shared memory needed.
#endif
}
- /* For internal workers set the entry point to known function address. */
- entrypt = GetInternalBgWorkerMain(worker);
-
/*
- * Otherwise, if bgw_main is set, we use that value as the initial
- * entrypoint. This does not work well EXEC_BACKEND outside Windows but
- * we keep the logic for backwards compatibility. In other cases use
- * the entry point specified by library name (which will be loaded, if
- * necessary) and a function name (which will be looked up in the named
- * library).
+ * If bgw_main is set, we use that value as the entry point function.
+ * Passing function addresses across processes is unreliable on many
+ * platforms, but we'll leave the option in place in 9.x for backwards
+ * compatibility. Otherwise, look up the entry point function, loading
+ * its library if necessary.
*/
- if (entrypt == NULL)
- {
- if (worker->bgw_main != NULL)
- entrypt = worker->bgw_main;
- else
- entrypt = (bgworker_main_type)
- load_external_function(worker->bgw_library_name,
- worker->bgw_function_name,
- true, NULL);
- }
+ if (worker->bgw_main != NULL)
+ entrypt = worker->bgw_main;
+ else
+ entrypt = LookupBackgroundWorkerFunction(worker->bgw_library_name,
+ worker->bgw_function_name);
/*
* Note that in normal processes, we would call InitPostgres here. For a
}
/*
- * Search the known internal worker array and return its main function
- * pointer if found.
+ * Look up (and possibly load) a bgworker entry point function.
*
- * Returns NULL if not known internal worker.
+ * For functions contained in the core code, we use library name "postgres"
+ * and consult the InternalBGWorkers array. External functions are
+ * looked up, and loaded if necessary, using load_external_function().
+ *
+ * The point of this is to pass function names as strings across process
+ * boundaries. We can't pass actual function addresses because of the
+ * possibility that the function has been loaded at a different address
+ * in a different process. This is obviously a hazard for functions in
+ * loadable libraries, but it can happen even for functions in the core code
+ * on platforms using EXEC_BACKEND (e.g., Windows).
+ *
+ * At some point it might be worthwhile to get rid of InternalBGWorkers[]
+ * in favor of applying load_external_function() for core functions too;
+ * but that raises portability issues that are not worth addressing now.
*/
static bgworker_main_type
-GetInternalBgWorkerMain(BackgroundWorker *worker)
+LookupBackgroundWorkerFunction(char *libraryname, char *funcname)
{
- int i;
+ /*
+ * If the function is to be loaded from postgres itself, search the
+ * InternalBGWorkers array.
+ */
+ if (strcmp(libraryname, "postgres") == 0)
+ {
+ int i;
- /* Internal workers always have to use postgres as library name. */
- if (strncmp(worker->bgw_library_name, "postgres", BGW_MAXLEN) != 0)
- return NULL;
+ for (i = 0; i < lengthof(InternalBGWorkers); i++)
+ {
+ if (strcmp(InternalBGWorkers[i].fn_name, funcname) == 0)
+ return InternalBGWorkers[i].fn_addr;
+ }
- for (i = 0; InternalBGWorkers[i].bgw_function_name; i++)
- {
- if (strncmp(InternalBGWorkers[i].bgw_function_name,
- worker->bgw_function_name, BGW_MAXLEN) == 0)
- return InternalBGWorkers[i].bgw_main;
+ /* We can only reach this by programming error. */
+ elog(ERROR, "internal function \"%s\" not found", funcname);
}
- return NULL;
+ /* Otherwise load from external library. */
+ return (bgworker_main_type)
+ load_external_function(libraryname, funcname, true, NULL);
}
projects / postgresql / commitdiff