#include "storage/dsm.h"
#include "storage/ipc.h"
#include "storage/lwlock.h"
+#include "storage/pg_shmem.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/resowner_private.h"
-#define PG_DYNSHMEM_STATE_FILE PG_DYNSHMEM_DIR "/state"
-#define PG_DYNSHMEM_NEW_STATE_FILE PG_DYNSHMEM_DIR "/state.new"
-#define PG_DYNSHMEM_STATE_BUFSIZ 512
#define PG_DYNSHMEM_CONTROL_MAGIC 0x9a503d32
/*
dsm_control_item item[FLEXIBLE_ARRAY_MEMBER];
} dsm_control_header;
-static void dsm_cleanup_using_control_segment(void);
static void dsm_cleanup_for_mmap(void);
-static bool dsm_read_state_file(dsm_handle *h);
-static void dsm_write_state_file(dsm_handle h);
static void dsm_postmaster_shutdown(int code, Datum arg);
static dsm_segment *dsm_create_descriptor(void);
static bool dsm_control_segment_sane(dsm_control_header *control,
* startup time.
*/
void
-dsm_postmaster_startup(void)
+dsm_postmaster_startup(PGShmemHeader *shim)
{
void *dsm_control_address = NULL;
uint32 maxitems;
return;
/*
- * Check for, and remove, shared memory segments left behind by a dead
- * postmaster. This isn't necessary on Windows, which always removes them
- * when the last reference is gone.
+ * If we're using the mmap implementations, clean up any leftovers.
+ * Cleanup isn't needed on Windows, and happens earlier in startup for
+ * POSIX and System V shared memory, via a direct call to
+ * dsm_cleanup_using_control_segment.
*/
- switch (dynamic_shared_memory_type)
- {
- case DSM_IMPL_POSIX:
- case DSM_IMPL_SYSV:
- dsm_cleanup_using_control_segment();
- break;
- case DSM_IMPL_MMAP:
- dsm_cleanup_for_mmap();
- break;
- case DSM_IMPL_WINDOWS:
- /* Nothing to do. */
- break;
- default:
- elog(ERROR, "unknown dynamic shared memory type: %d",
- dynamic_shared_memory_type);
- }
+ if (dynamic_shared_memory_type == DSM_IMPL_MMAP)
+ dsm_cleanup_for_mmap();
/* Determine size for new control segment. */
maxitems = PG_DYNSHMEM_FIXED_SLOTS
maxitems);
segsize = dsm_control_bytes_needed(maxitems);
- /* Loop until we find an unused identifier for the new control segment. */
+ /*
+ * Loop until we find an unused identifier for the new control segment.
+ * We sometimes use 0 as a sentinel value indicating that no control
+ * segment is known to exist, so avoid using that value for a real
+ * control segment.
+ */
for (;;)
{
Assert(dsm_control_address == NULL);
Assert(dsm_control_mapped_size == 0);
dsm_control_handle = random();
+ if (dsm_control_handle == 0)
+ continue;
if (dsm_impl_op(DSM_OP_CREATE, dsm_control_handle, segsize,
&dsm_control_impl_private, &dsm_control_address,
&dsm_control_mapped_size, ERROR))
break;
}
dsm_control = dsm_control_address;
- on_shmem_exit(dsm_postmaster_shutdown, 0);
+ on_shmem_exit(dsm_postmaster_shutdown, PointerGetDatum(shim));
elog(DEBUG2,
"created dynamic shared memory control segment %u (%zu bytes)",
dsm_control_handle, segsize);
- dsm_write_state_file(dsm_control_handle);
+ shim->dsm_control = dsm_control_handle;
/* Initialize control segment. */
dsm_control->magic = PG_DYNSHMEM_CONTROL_MAGIC;
* invocation still exists. If so, remove the dynamic shared memory
* segments to which it refers, and then the control segment itself.
*/
-static void
-dsm_cleanup_using_control_segment(void)
+void
+dsm_cleanup_using_control_segment(dsm_handle old_control_handle)
{
void *mapped_address = NULL;
void *junk_mapped_address = NULL;
Size junk_mapped_size = 0;
uint32 nitems;
uint32 i;
- dsm_handle old_control_handle;
dsm_control_header *old_control;
- /*
- * Read the state file. If it doesn't exist or is empty, there's nothing
- * more to do.
- */
- if (!dsm_read_state_file(&old_control_handle))
+ /* If dynamic shared memory is disabled, there's nothing to do. */
+ if (dynamic_shared_memory_type == DSM_IMPL_NONE)
return;
/*
FreeDir(dir);
}
-/*
- * Read and parse the state file.
- *
- * If the state file is empty or the contents are garbled, it probably means
- * that the operating system rebooted before the data written by the previous
- * postmaster made it to disk. In that case, we can just ignore it; any shared
- * memory from before the reboot should be gone anyway.
- */
-static bool
-dsm_read_state_file(dsm_handle *h)
-{
- int statefd;
- char statebuf[PG_DYNSHMEM_STATE_BUFSIZ];
- int nbytes = 0;
- char *endptr,
- *s;
- dsm_handle handle;
-
- /* Read the state file to get the ID of the old control segment. */
- statefd = BasicOpenFile(PG_DYNSHMEM_STATE_FILE, O_RDONLY | PG_BINARY, 0);
- if (statefd < 0)
- {
- if (errno == ENOENT)
- return false;
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not open file \"%s\": %m",
- PG_DYNSHMEM_STATE_FILE)));
- }
- nbytes = read(statefd, statebuf, PG_DYNSHMEM_STATE_BUFSIZ - 1);
- if (nbytes < 0)
- {
- close(statefd);
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not read file \"%s\": %m",
- PG_DYNSHMEM_STATE_FILE)));
- }
- /* make sure buffer is NUL terminated */
- statebuf[nbytes] = '\0';
- close(statefd);
-
- /*
- * We expect to find the handle of the old control segment here,
- * on a line by itself.
- */
- handle = strtoul(statebuf, &endptr, 10);
- for (s = endptr; *s == ' ' || *s == '\t'; ++s)
- ;
- if (*s != '\n' && *s != '\0')
- return false;
-
- /* Looks good. */
- *h = handle;
- return true;
-}
-
-/*
- * Write our control segment handle to the state file, so that if the
- * postmaster is killed without running it's on_shmem_exit hooks, the
- * next postmaster can clean things up after restart.
- */
-static void
-dsm_write_state_file(dsm_handle h)
-{
- int statefd;
- char statebuf[PG_DYNSHMEM_STATE_BUFSIZ];
- int nbytes;
-
- /* Create or truncate the file. */
- statefd = open(PG_DYNSHMEM_NEW_STATE_FILE,
- O_RDWR | O_CREAT | O_TRUNC | PG_BINARY, 0600);
- if (statefd < 0)
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not create file \"%s\": %m",
- PG_DYNSHMEM_NEW_STATE_FILE)));
-
- /* Write contents. */
- snprintf(statebuf, PG_DYNSHMEM_STATE_BUFSIZ, "%u\n", dsm_control_handle);
- nbytes = strlen(statebuf);
- if (write(statefd, statebuf, nbytes) != nbytes)
- {
- if (errno == 0)
- errno = ENOSPC; /* if no error signalled, assume no space */
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not write file \"%s\": %m",
- PG_DYNSHMEM_NEW_STATE_FILE)));
- }
-
- /* Close file. */
- close(statefd);
-
- /*
- * Atomically rename file into place, so that no one ever sees a partially
- * written state file.
- */
- if (rename(PG_DYNSHMEM_NEW_STATE_FILE, PG_DYNSHMEM_STATE_FILE) < 0)
- ereport(ERROR,
- (errcode_for_file_access(),
- errmsg("could not rename file \"%s\": %m",
- PG_DYNSHMEM_NEW_STATE_FILE)));
-}
-
/*
* At shutdown time, we iterate over the control segment and remove all
* remaining dynamic shared memory segments. We avoid throwing errors here;
void *junk_mapped_address = NULL;
void *junk_impl_private = NULL;
Size junk_mapped_size = 0;
+ PGShmemHeader *shim = (PGShmemHeader *) DatumGetPointer(arg);
/*
* If some other backend exited uncleanly, it might have corrupted the
&dsm_control_impl_private, &dsm_control_address,
&dsm_control_mapped_size, LOG);
dsm_control = dsm_control_address;
-
- /* And, finally, remove the state file. */
- if (unlink(PG_DYNSHMEM_STATE_FILE) < 0)
- ereport(LOG,
- (errcode_for_file_access(),
- errmsg("could not unlink file \"%s\": %m",
- PG_DYNSHMEM_STATE_FILE)));
+ shim->dsm_control = 0;
}
/*
#ifdef EXEC_BACKEND
{
- dsm_handle control_handle;
void *control_address = NULL;
- /* Read the control segment information from the state file. */
- if (!dsm_read_state_file(&control_handle))
- ereport(ERROR,
- (errcode(ERRCODE_INTERNAL_ERROR),
- errmsg("could not parse dynamic shared memory state file")));
-
/* Attach control segment. */
- dsm_impl_op(DSM_OP_ATTACH, control_handle, 0,
+ Assert(dsm_control_handle != 0);
+ dsm_impl_op(DSM_OP_ATTACH, dsm_control_handle, 0,
&dsm_control_impl_private, &control_address,
&dsm_control_mapped_size, ERROR);
- dsm_control_handle = control_handle;
dsm_control = control_address;
/* If control segment doesn't look sane, something is badly wrong. */
if (!dsm_control_segment_sane(dsm_control, dsm_control_mapped_size))
{
- dsm_impl_op(DSM_OP_DETACH, control_handle, 0,
+ dsm_impl_op(DSM_OP_DETACH, dsm_control_handle, 0,
&dsm_control_impl_private, &control_address,
&dsm_control_mapped_size, WARNING);
ereport(FATAL,
dsm_init_done = true;
}
+#ifdef EXEC_BACKEND
+/*
+ * When running under EXEC_BACKEND, we get a callback here when the main
+ * shared memory segment is re-attached, so that we can record the control
+ * handle retrieved from it.
+ */
+void
+dsm_set_control_handle(dsm_handle h)
+{
+ Assert(dsm_control_handle == 0 && h != 0);
+ dsm_control_handle = h;
+}
+#endif
+
/*
* Create a new dynamic shared memory segment.
*/
projects / postgresql / commitdiff