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dsm.h File Reference
#include "storage/dsm_impl.h"
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Macros

#define DSM_CREATE_NULL_IF_MAXSEGMENTS   0x0001
 

Typedefs

typedef struct dsm_segment dsm_segment
 
typedef void(* on_dsm_detach_callback) (dsm_segment *, Datum arg)
 

Functions

void dsm_cleanup_using_control_segment (dsm_handle old_control_handle)
 
void dsm_postmaster_startup (struct PGShmemHeader *)
 
void dsm_backend_shutdown (void)
 
void dsm_detach_all (void)
 
size_t dsm_estimate_size (void)
 
void dsm_shmem_init (void)
 
dsm_segmentdsm_create (Size size, int flags)
 
dsm_segmentdsm_attach (dsm_handle h)
 
void dsm_detach (dsm_segment *seg)
 
void dsm_pin_mapping (dsm_segment *seg)
 
void dsm_unpin_mapping (dsm_segment *seg)
 
void dsm_pin_segment (dsm_segment *seg)
 
void dsm_unpin_segment (dsm_handle handle)
 
dsm_segmentdsm_find_mapping (dsm_handle handle)
 
void * dsm_segment_address (dsm_segment *seg)
 
Size dsm_segment_map_length (dsm_segment *seg)
 
dsm_handle dsm_segment_handle (dsm_segment *seg)
 
void on_dsm_detach (dsm_segment *seg, on_dsm_detach_callback function, Datum arg)
 
void cancel_on_dsm_detach (dsm_segment *seg, on_dsm_detach_callback function, Datum arg)
 
void reset_on_dsm_detach (void)
 

Macro Definition Documentation

◆ DSM_CREATE_NULL_IF_MAXSEGMENTS

#define DSM_CREATE_NULL_IF_MAXSEGMENTS   0x0001

Definition at line 20 of file dsm.h.

Typedef Documentation

◆ dsm_segment

typedef struct dsm_segment dsm_segment

Definition at line 1 of file dsm.h.

◆ on_dsm_detach_callback

typedef void(* on_dsm_detach_callback) (dsm_segment *, Datum arg)

Definition at line 54 of file dsm.h.

Function Documentation

◆ cancel_on_dsm_detach()

void cancel_on_dsm_detach ( dsm_segment seg,
on_dsm_detach_callback  function,
Datum  arg 
)

Definition at line 1147 of file dsm.c.

1149 {
1150  slist_mutable_iter iter;
1151 
1152  slist_foreach_modify(iter, &seg->on_detach)
1153  {
1155 
1157  if (cb->function == function && cb->arg == arg)
1158  {
1159  slist_delete_current(&iter);
1160  pfree(cb);
1161  break;
1162  }
1163  }
1164 }
static void slist_delete_current(slist_mutable_iter *iter)
Definition: ilist.h:1084
#define slist_foreach_modify(iter, lhead)
Definition: ilist.h:1148
#define slist_container(type, membername, ptr)
Definition: ilist.h:1106
void pfree(void *pointer)
Definition: mcxt.c:1520
void * arg
on_dsm_detach_callback function
Definition: dsm.c:60
slist_head on_detach
Definition: dsm.c:75
slist_node * cur
Definition: ilist.h:274

References dsm_segment_detach_callback::arg, arg, slist_mutable_iter::cur, dsm_segment_detach_callback::function, dsm_segment::on_detach, pfree(), slist_container, slist_delete_current(), and slist_foreach_modify.

Referenced by shm_mq_detach(), and test_shm_mq_setup().

◆ dsm_attach()

dsm_segment* dsm_attach ( dsm_handle  h)

Definition at line 665 of file dsm.c.

666 {
667  dsm_segment *seg;
668  dlist_iter iter;
669  uint32 i;
670  uint32 nitems;
671 
672  /* Unsafe in postmaster (and pointless in a stand-alone backend). */
674 
675  if (!dsm_init_done)
677 
678  /*
679  * Since this is just a debugging cross-check, we could leave it out
680  * altogether, or include it only in assert-enabled builds. But since the
681  * list of attached segments should normally be very short, let's include
682  * it always for right now.
683  *
684  * If you're hitting this error, you probably want to attempt to find an
685  * existing mapping via dsm_find_mapping() before calling dsm_attach() to
686  * create a new one.
687  */
689  {
690  seg = dlist_container(dsm_segment, node, iter.cur);
691  if (seg->handle == h)
692  elog(ERROR, "can't attach the same segment more than once");
693  }
694 
695  /* Create a new segment descriptor. */
696  seg = dsm_create_descriptor();
697  seg->handle = h;
698 
699  /* Bump reference count for this segment in shared memory. */
700  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
702  for (i = 0; i < nitems; ++i)
703  {
704  /*
705  * If the reference count is 0, the slot is actually unused. If the
706  * reference count is 1, the slot is still in use, but the segment is
707  * in the process of going away; even if the handle matches, another
708  * slot may already have started using the same handle value by
709  * coincidence so we have to keep searching.
710  */
711  if (dsm_control->item[i].refcnt <= 1)
712  continue;
713 
714  /* If the handle doesn't match, it's not the slot we want. */
715  if (dsm_control->item[i].handle != seg->handle)
716  continue;
717 
718  /* Otherwise we've found a match. */
719  dsm_control->item[i].refcnt++;
720  seg->control_slot = i;
722  {
723  seg->mapped_address = (char *) dsm_main_space_begin +
726  }
727  break;
728  }
729  LWLockRelease(DynamicSharedMemoryControlLock);
730 
731  /*
732  * If we didn't find the handle we're looking for in the control segment,
733  * it probably means that everyone else who had it mapped, including the
734  * original creator, died before we got to this point. It's up to the
735  * caller to decide what to do about that.
736  */
738  {
739  dsm_detach(seg);
740  return NULL;
741  }
742 
743  /* Here's where we actually try to map the segment. */
746  &seg->mapped_address, &seg->mapped_size, ERROR);
747 
748  return seg;
749 }
unsigned int uint32
Definition: c.h:506
#define Assert(condition)
Definition: c.h:858
static void dsm_backend_startup(void)
Definition: dsm.c:423
static void * dsm_main_space_begin
Definition: dsm.c:111
void dsm_detach(dsm_segment *seg)
Definition: dsm.c:803
static dlist_head dsm_segment_list
Definition: dsm.c:130
static bool dsm_init_done
Definition: dsm.c:108
static dsm_control_header * dsm_control
Definition: dsm.c:140
static dsm_segment * dsm_create_descriptor(void)
Definition: dsm.c:1201
#define INVALID_CONTROL_SLOT
Definition: dsm.c:55
static bool is_main_region_dsm_handle(dsm_handle handle)
Definition: dsm.c:1281
bool dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size, void **impl_private, void **mapped_address, Size *mapped_size, int elevel)
Definition: dsm_impl.c:159
@ DSM_OP_ATTACH
Definition: dsm_impl.h:64
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:224
#define FPM_PAGE_SIZE
Definition: freepage.h:30
bool IsUnderPostmaster
Definition: globals.c:117
#define dlist_foreach(iter, lhead)
Definition: ilist.h:623
#define dlist_container(type, membername, ptr)
Definition: ilist.h:593
#define nitems(x)
Definition: indent.h:31
int i
Definition: isn.c:73
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1170
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1783
@ LW_EXCLUSIVE
Definition: lwlock.h:114
dlist_node * cur
Definition: ilist.h:179
uint32 nitems
Definition: dsm.c:93
dsm_control_item item[FLEXIBLE_ARRAY_MEMBER]
Definition: dsm.c:95
size_t npages
Definition: dsm.c:84
dsm_handle handle
Definition: dsm.c:81
size_t first_page
Definition: dsm.c:83
uint32 refcnt
Definition: dsm.c:82
uint32 control_slot
Definition: dsm.c:71
dsm_handle handle
Definition: dsm.c:70
Size mapped_size
Definition: dsm.c:74
void * impl_private
Definition: dsm.c:72
void * mapped_address
Definition: dsm.c:73

References Assert, dsm_segment::control_slot, dlist_iter::cur, dlist_container, dlist_foreach, dsm_backend_startup(), dsm_control, dsm_create_descriptor(), dsm_detach(), dsm_impl_op(), dsm_init_done, dsm_main_space_begin, DSM_OP_ATTACH, dsm_segment_list, elog, ERROR, dsm_control_item::first_page, FPM_PAGE_SIZE, dsm_segment::handle, dsm_control_item::handle, i, dsm_segment::impl_private, INVALID_CONTROL_SLOT, is_main_region_dsm_handle(), IsUnderPostmaster, dsm_control_header::item, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), dsm_segment::mapped_address, dsm_segment::mapped_size, dsm_control_header::nitems, nitems, dsm_control_item::npages, and dsm_control_item::refcnt.

Referenced by AttachSession(), autoprewarm_database_main(), dsa_attach(), get_segment_by_index(), GetNamedDSMSegment(), ParallelApplyWorkerMain(), ParallelWorkerMain(), and test_shm_mq_main().

◆ dsm_backend_shutdown()

void dsm_backend_shutdown ( void  )

Definition at line 757 of file dsm.c.

758 {
760  {
761  dsm_segment *seg;
762 
764  dsm_detach(seg);
765  }
766 }
#define dlist_head_element(type, membername, lhead)
Definition: ilist.h:603
static bool dlist_is_empty(const dlist_head *head)
Definition: ilist.h:336

References dlist_head_element, dlist_is_empty(), dsm_detach(), and dsm_segment_list.

Referenced by shmem_exit().

◆ dsm_cleanup_using_control_segment()

void dsm_cleanup_using_control_segment ( dsm_handle  old_control_handle)

Definition at line 238 of file dsm.c.

239 {
240  void *mapped_address = NULL;
241  void *junk_mapped_address = NULL;
242  void *impl_private = NULL;
243  void *junk_impl_private = NULL;
244  Size mapped_size = 0;
245  Size junk_mapped_size = 0;
246  uint32 nitems;
247  uint32 i;
248  dsm_control_header *old_control;
249 
250  /*
251  * Try to attach the segment. If this fails, it probably just means that
252  * the operating system has been rebooted and the segment no longer
253  * exists, or an unrelated process has used the same shm ID. So just fall
254  * out quietly.
255  */
256  if (!dsm_impl_op(DSM_OP_ATTACH, old_control_handle, 0, &impl_private,
257  &mapped_address, &mapped_size, DEBUG1))
258  return;
259 
260  /*
261  * We've managed to reattach it, but the contents might not be sane. If
262  * they aren't, we disregard the segment after all.
263  */
264  old_control = (dsm_control_header *) mapped_address;
265  if (!dsm_control_segment_sane(old_control, mapped_size))
266  {
267  dsm_impl_op(DSM_OP_DETACH, old_control_handle, 0, &impl_private,
268  &mapped_address, &mapped_size, LOG);
269  return;
270  }
271 
272  /*
273  * OK, the control segment looks basically valid, so we can use it to get
274  * a list of segments that need to be removed.
275  */
276  nitems = old_control->nitems;
277  for (i = 0; i < nitems; ++i)
278  {
279  dsm_handle handle;
280  uint32 refcnt;
281 
282  /* If the reference count is 0, the slot is actually unused. */
283  refcnt = old_control->item[i].refcnt;
284  if (refcnt == 0)
285  continue;
286 
287  /* If it was using the main shmem area, there is nothing to do. */
288  handle = old_control->item[i].handle;
289  if (is_main_region_dsm_handle(handle))
290  continue;
291 
292  /* Log debugging information. */
293  elog(DEBUG2, "cleaning up orphaned dynamic shared memory with ID %u (reference count %u)",
294  handle, refcnt);
295 
296  /* Destroy the referenced segment. */
297  dsm_impl_op(DSM_OP_DESTROY, handle, 0, &junk_impl_private,
298  &junk_mapped_address, &junk_mapped_size, LOG);
299  }
300 
301  /* Destroy the old control segment, too. */
302  elog(DEBUG2,
303  "cleaning up dynamic shared memory control segment with ID %u",
304  old_control_handle);
305  dsm_impl_op(DSM_OP_DESTROY, old_control_handle, 0, &impl_private,
306  &mapped_address, &mapped_size, LOG);
307 }
size_t Size
Definition: c.h:605
static bool dsm_control_segment_sane(dsm_control_header *control, Size mapped_size)
Definition: dsm.c:1237
uint32 dsm_handle
Definition: dsm_impl.h:55
@ DSM_OP_DETACH
Definition: dsm_impl.h:65
@ DSM_OP_DESTROY
Definition: dsm_impl.h:66
#define LOG
Definition: elog.h:31
#define DEBUG2
Definition: elog.h:29
#define DEBUG1
Definition: elog.h:30

References DEBUG1, DEBUG2, dsm_control_segment_sane(), dsm_impl_op(), DSM_OP_ATTACH, DSM_OP_DESTROY, DSM_OP_DETACH, elog, dsm_control_item::handle, i, is_main_region_dsm_handle(), dsm_control_header::item, LOG, dsm_control_header::nitems, nitems, and dsm_control_item::refcnt.

Referenced by PGSharedMemoryCreate().

◆ dsm_create()

dsm_segment* dsm_create ( Size  size,
int  flags 
)

Definition at line 516 of file dsm.c.

517 {
518  dsm_segment *seg;
519  uint32 i;
520  uint32 nitems;
521  size_t npages = 0;
522  size_t first_page = 0;
523  FreePageManager *dsm_main_space_fpm = dsm_main_space_begin;
524  bool using_main_dsm_region = false;
525 
526  /*
527  * Unsafe in postmaster. It might seem pointless to allow use of dsm in
528  * single user mode, but otherwise some subsystems will need dedicated
529  * single user mode code paths.
530  */
532 
533  if (!dsm_init_done)
535 
536  /* Create a new segment descriptor. */
537  seg = dsm_create_descriptor();
538 
539  /*
540  * Lock the control segment while we try to allocate from the main shared
541  * memory area, if configured.
542  */
543  if (dsm_main_space_fpm)
544  {
545  npages = size / FPM_PAGE_SIZE;
546  if (size % FPM_PAGE_SIZE > 0)
547  ++npages;
548 
549  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
550  if (FreePageManagerGet(dsm_main_space_fpm, npages, &first_page))
551  {
552  /* We can carve out a piece of the main shared memory segment. */
553  seg->mapped_address = (char *) dsm_main_space_begin +
554  first_page * FPM_PAGE_SIZE;
555  seg->mapped_size = npages * FPM_PAGE_SIZE;
556  using_main_dsm_region = true;
557  /* We'll choose a handle below. */
558  }
559  }
560 
561  if (!using_main_dsm_region)
562  {
563  /*
564  * We need to create a new memory segment. Loop until we find an
565  * unused segment identifier.
566  */
567  if (dsm_main_space_fpm)
568  LWLockRelease(DynamicSharedMemoryControlLock);
569  for (;;)
570  {
571  Assert(seg->mapped_address == NULL && seg->mapped_size == 0);
572  /* Use even numbers only */
574  if (seg->handle == DSM_HANDLE_INVALID) /* Reserve sentinel */
575  continue;
577  &seg->mapped_address, &seg->mapped_size, ERROR))
578  break;
579  }
580  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
581  }
582 
583  /* Search the control segment for an unused slot. */
585  for (i = 0; i < nitems; ++i)
586  {
587  if (dsm_control->item[i].refcnt == 0)
588  {
589  if (using_main_dsm_region)
590  {
592  dsm_control->item[i].first_page = first_page;
593  dsm_control->item[i].npages = npages;
594  }
595  else
597  dsm_control->item[i].handle = seg->handle;
598  /* refcnt of 1 triggers destruction, so start at 2 */
599  dsm_control->item[i].refcnt = 2;
601  dsm_control->item[i].pinned = false;
602  seg->control_slot = i;
603  LWLockRelease(DynamicSharedMemoryControlLock);
604  return seg;
605  }
606  }
607 
608  /* Verify that we can support an additional mapping. */
609  if (nitems >= dsm_control->maxitems)
610  {
611  if (using_main_dsm_region)
612  FreePageManagerPut(dsm_main_space_fpm, first_page, npages);
613  LWLockRelease(DynamicSharedMemoryControlLock);
614  if (!using_main_dsm_region)
616  &seg->mapped_address, &seg->mapped_size, WARNING);
617  if (seg->resowner != NULL)
618  ResourceOwnerForgetDSM(seg->resowner, seg);
619  dlist_delete(&seg->node);
620  pfree(seg);
621 
622  if ((flags & DSM_CREATE_NULL_IF_MAXSEGMENTS) != 0)
623  return NULL;
624  ereport(ERROR,
625  (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
626  errmsg("too many dynamic shared memory segments")));
627  }
628 
629  /* Enter the handle into a new array slot. */
630  if (using_main_dsm_region)
631  {
633  dsm_control->item[i].first_page = first_page;
634  dsm_control->item[i].npages = npages;
635  }
637  /* refcnt of 1 triggers destruction, so start at 2 */
640  dsm_control->item[nitems].pinned = false;
641  seg->control_slot = nitems;
642  dsm_control->nitems++;
643  LWLockRelease(DynamicSharedMemoryControlLock);
644 
645  return seg;
646 }
static void ResourceOwnerForgetDSM(ResourceOwner owner, dsm_segment *seg)
Definition: dsm.c:165
static dsm_handle make_main_region_dsm_handle(int slot)
Definition: dsm.c:1262
#define DSM_CREATE_NULL_IF_MAXSEGMENTS
Definition: dsm.h:20
@ DSM_OP_CREATE
Definition: dsm_impl.h:63
#define DSM_HANDLE_INVALID
Definition: dsm_impl.h:58
int errcode(int sqlerrcode)
Definition: elog.c:857
int errmsg(const char *fmt,...)
Definition: elog.c:1070
#define WARNING
Definition: elog.h:36
#define ereport(elevel,...)
Definition: elog.h:149
bool FreePageManagerGet(FreePageManager *fpm, Size npages, Size *first_page)
Definition: freepage.c:210
void FreePageManagerPut(FreePageManager *fpm, Size first_page, Size npages)
Definition: freepage.c:379
bool IsPostmasterEnvironment
Definition: globals.c:116
static void dlist_delete(dlist_node *node)
Definition: ilist.h:405
uint32 pg_prng_uint32(pg_prng_state *state)
Definition: pg_prng.c:227
pg_prng_state pg_global_prng_state
Definition: pg_prng.c:34
static pg_noinline void Size size
Definition: slab.c:607
uint32 maxitems
Definition: dsm.c:94
bool pinned
Definition: dsm.c:86
void * impl_private_pm_handle
Definition: dsm.c:85
dlist_node node
Definition: dsm.c:68
ResourceOwner resowner
Definition: dsm.c:69

References Assert, dsm_segment::control_slot, dlist_delete(), dsm_backend_startup(), dsm_control, dsm_create_descriptor(), DSM_CREATE_NULL_IF_MAXSEGMENTS, DSM_HANDLE_INVALID, dsm_impl_op(), dsm_init_done, dsm_main_space_begin, DSM_OP_CREATE, DSM_OP_DESTROY, ereport, errcode(), errmsg(), ERROR, dsm_control_item::first_page, FPM_PAGE_SIZE, FreePageManagerGet(), FreePageManagerPut(), dsm_segment::handle, dsm_control_item::handle, i, dsm_segment::impl_private, dsm_control_item::impl_private_pm_handle, is_main_region_dsm_handle(), IsPostmasterEnvironment, IsUnderPostmaster, dsm_control_header::item, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), make_main_region_dsm_handle(), dsm_segment::mapped_address, dsm_segment::mapped_size, dsm_control_header::maxitems, dsm_control_header::nitems, nitems, dsm_segment::node, dsm_control_item::npages, pfree(), pg_global_prng_state, pg_prng_uint32(), dsm_control_item::pinned, dsm_control_item::refcnt, ResourceOwnerForgetDSM(), dsm_segment::resowner, size, and WARNING.

Referenced by apw_load_buffers(), dsa_create_ext(), GetNamedDSMSegment(), GetSessionDsmHandle(), InitializeParallelDSM(), make_new_segment(), pa_setup_dsm(), and setup_dynamic_shared_memory().

◆ dsm_detach()

void dsm_detach ( dsm_segment seg)

Definition at line 803 of file dsm.c.

804 {
805  /*
806  * Invoke registered callbacks. Just in case one of those callbacks
807  * throws a further error that brings us back here, pop the callback
808  * before invoking it, to avoid infinite error recursion. Don't allow
809  * interrupts while running the individual callbacks in non-error code
810  * paths, to avoid leaving cleanup work unfinished if we're interrupted by
811  * a statement timeout or similar.
812  */
813  HOLD_INTERRUPTS();
814  while (!slist_is_empty(&seg->on_detach))
815  {
816  slist_node *node;
818  on_dsm_detach_callback function;
819  Datum arg;
820 
821  node = slist_pop_head_node(&seg->on_detach);
823  function = cb->function;
824  arg = cb->arg;
825  pfree(cb);
826 
827  function(seg, arg);
828  }
830 
831  /*
832  * Try to remove the mapping, if one exists. Normally, there will be, but
833  * maybe not, if we failed partway through a create or attach operation.
834  * We remove the mapping before decrementing the reference count so that
835  * the process that sees a zero reference count can be certain that no
836  * remaining mappings exist. Even if this fails, we pretend that it
837  * works, because retrying is likely to fail in the same way.
838  */
839  if (seg->mapped_address != NULL)
840  {
843  &seg->mapped_address, &seg->mapped_size, WARNING);
844  seg->impl_private = NULL;
845  seg->mapped_address = NULL;
846  seg->mapped_size = 0;
847  }
848 
849  /* Reduce reference count, if we previously increased it. */
851  {
852  uint32 refcnt;
853  uint32 control_slot = seg->control_slot;
854 
855  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
856  Assert(dsm_control->item[control_slot].handle == seg->handle);
857  Assert(dsm_control->item[control_slot].refcnt > 1);
858  refcnt = --dsm_control->item[control_slot].refcnt;
860  LWLockRelease(DynamicSharedMemoryControlLock);
861 
862  /* If new reference count is 1, try to destroy the segment. */
863  if (refcnt == 1)
864  {
865  /* A pinned segment should never reach 1. */
866  Assert(!dsm_control->item[control_slot].pinned);
867 
868  /*
869  * If we fail to destroy the segment here, or are killed before we
870  * finish doing so, the reference count will remain at 1, which
871  * will mean that nobody else can attach to the segment. At
872  * postmaster shutdown time, or when a new postmaster is started
873  * after a hard kill, another attempt will be made to remove the
874  * segment.
875  *
876  * The main case we're worried about here is being killed by a
877  * signal before we can finish removing the segment. In that
878  * case, it's important to be sure that the segment still gets
879  * removed. If we actually fail to remove the segment for some
880  * other reason, the postmaster may not have any better luck than
881  * we did. There's not much we can do about that, though.
882  */
883  if (is_main_region_dsm_handle(seg->handle) ||
885  &seg->mapped_address, &seg->mapped_size, WARNING))
886  {
887  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
890  dsm_control->item[control_slot].first_page,
891  dsm_control->item[control_slot].npages);
892  Assert(dsm_control->item[control_slot].handle == seg->handle);
893  Assert(dsm_control->item[control_slot].refcnt == 1);
894  dsm_control->item[control_slot].refcnt = 0;
895  LWLockRelease(DynamicSharedMemoryControlLock);
896  }
897  }
898  }
899 
900  /* Clean up our remaining backend-private data structures. */
901  if (seg->resowner != NULL)
902  ResourceOwnerForgetDSM(seg->resowner, seg);
903  dlist_delete(&seg->node);
904  pfree(seg);
905 }
void(* on_dsm_detach_callback)(dsm_segment *, Datum arg)
Definition: dsm.h:54
static bool slist_is_empty(const slist_head *head)
Definition: ilist.h:995
static slist_node * slist_pop_head_node(slist_head *head)
Definition: ilist.h:1028
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:135
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:133
uintptr_t Datum
Definition: postgres.h:64

References dsm_segment_detach_callback::arg, arg, Assert, dsm_segment::control_slot, dlist_delete(), dsm_control, dsm_impl_op(), dsm_main_space_begin, DSM_OP_DESTROY, DSM_OP_DETACH, dsm_control_item::first_page, FreePageManagerPut(), dsm_segment_detach_callback::function, dsm_segment::handle, dsm_control_item::handle, HOLD_INTERRUPTS, dsm_segment::impl_private, INVALID_CONTROL_SLOT, is_main_region_dsm_handle(), dsm_control_header::item, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), dsm_segment::mapped_address, dsm_segment::mapped_size, dsm_segment::node, dsm_control_item::npages, dsm_segment::on_detach, pfree(), dsm_control_item::pinned, dsm_control_item::refcnt, ResourceOwnerForgetDSM(), dsm_segment::resowner, RESUME_INTERRUPTS, slist_container, slist_is_empty(), slist_pop_head_node(), and WARNING.

Referenced by apw_load_buffers(), autoprewarm_database_main(), check_for_freed_segments_locked(), destroy_superblock(), DestroyParallelContext(), DetachSession(), dsa_detach(), dsm_attach(), dsm_backend_shutdown(), dsm_detach_all(), pa_free_worker_info(), pa_shutdown(), ParallelWorkerShutdown(), ResOwnerReleaseDSM(), test_shm_mq(), test_shm_mq_main(), and test_shm_mq_pipelined().

◆ dsm_detach_all()

void dsm_detach_all ( void  )

Definition at line 775 of file dsm.c.

776 {
777  void *control_address = dsm_control;
778 
780  {
781  dsm_segment *seg;
782 
784  dsm_detach(seg);
785  }
786 
787  if (control_address != NULL)
789  &dsm_control_impl_private, &control_address,
791 }
static dsm_handle dsm_control_handle
Definition: dsm.c:139
static Size dsm_control_mapped_size
Definition: dsm.c:141
static void * dsm_control_impl_private
Definition: dsm.c:142

References dlist_head_element, dlist_is_empty(), dsm_control, dsm_control_handle, dsm_control_impl_private, dsm_control_mapped_size, dsm_detach(), dsm_impl_op(), DSM_OP_DETACH, dsm_segment_list, and ERROR.

◆ dsm_estimate_size()

size_t dsm_estimate_size ( void  )

Definition at line 470 of file dsm.c.

471 {
472  return 1024 * 1024 * (size_t) min_dynamic_shared_memory;
473 }
int min_dynamic_shared_memory
Definition: dsm_impl.c:115

References min_dynamic_shared_memory.

Referenced by CalculateShmemSize(), and dsm_shmem_init().

◆ dsm_find_mapping()

dsm_segment* dsm_find_mapping ( dsm_handle  handle)

Definition at line 1076 of file dsm.c.

1077 {
1078  dlist_iter iter;
1079  dsm_segment *seg;
1080 
1082  {
1083  seg = dlist_container(dsm_segment, node, iter.cur);
1084  if (seg->handle == handle)
1085  return seg;
1086  }
1087 
1088  return NULL;
1089 }

References dlist_iter::cur, dlist_container, dlist_foreach, dsm_segment_list, and dsm_segment::handle.

Referenced by GetNamedDSMSegment().

◆ dsm_pin_mapping()

void dsm_pin_mapping ( dsm_segment seg)

Definition at line 915 of file dsm.c.

916 {
917  if (seg->resowner != NULL)
918  {
919  ResourceOwnerForgetDSM(seg->resowner, seg);
920  seg->resowner = NULL;
921  }
922 }

References ResourceOwnerForgetDSM(), and dsm_segment::resowner.

Referenced by AttachSession(), dsa_pin_mapping(), GetNamedDSMSegment(), and GetSessionDsmHandle().

◆ dsm_pin_segment()

void dsm_pin_segment ( dsm_segment seg)

Definition at line 955 of file dsm.c.

956 {
957  void *handle = NULL;
958 
959  /*
960  * Bump reference count for this segment in shared memory. This will
961  * ensure that even if there is no session which is attached to this
962  * segment, it will remain until postmaster shutdown or an explicit call
963  * to unpin.
964  */
965  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
966  if (dsm_control->item[seg->control_slot].pinned)
967  elog(ERROR, "cannot pin a segment that is already pinned");
969  dsm_impl_pin_segment(seg->handle, seg->impl_private, &handle);
970  dsm_control->item[seg->control_slot].pinned = true;
973  LWLockRelease(DynamicSharedMemoryControlLock);
974 }
void dsm_impl_pin_segment(dsm_handle handle, void *impl_private, void **impl_private_pm_handle)
Definition: dsm_impl.c:963

References dsm_segment::control_slot, dsm_control, dsm_impl_pin_segment(), elog, ERROR, dsm_segment::handle, dsm_segment::impl_private, dsm_control_item::impl_private_pm_handle, is_main_region_dsm_handle(), dsm_control_header::item, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), dsm_control_item::pinned, and dsm_control_item::refcnt.

Referenced by dsa_create_ext(), GetNamedDSMSegment(), and make_new_segment().

◆ dsm_postmaster_startup()

void dsm_postmaster_startup ( struct PGShmemHeader shim)

Definition at line 177 of file dsm.c.

178 {
179  void *dsm_control_address = NULL;
180  uint32 maxitems;
181  Size segsize;
182 
184 
185  /*
186  * If we're using the mmap implementations, clean up any leftovers.
187  * Cleanup isn't needed on Windows, and happens earlier in startup for
188  * POSIX and System V shared memory, via a direct call to
189  * dsm_cleanup_using_control_segment.
190  */
193 
194  /* Determine size for new control segment. */
195  maxitems = PG_DYNSHMEM_FIXED_SLOTS
197  elog(DEBUG2, "dynamic shared memory system will support %u segments",
198  maxitems);
199  segsize = dsm_control_bytes_needed(maxitems);
200 
201  /*
202  * Loop until we find an unused identifier for the new control segment. We
203  * sometimes use DSM_HANDLE_INVALID as a sentinel value indicating "no
204  * control segment", so avoid generating that value for a real handle.
205  */
206  for (;;)
207  {
208  Assert(dsm_control_address == NULL);
210  /* Use even numbers only */
213  continue;
215  &dsm_control_impl_private, &dsm_control_address,
217  break;
218  }
219  dsm_control = dsm_control_address;
221  elog(DEBUG2,
222  "created dynamic shared memory control segment %u (%zu bytes)",
223  dsm_control_handle, segsize);
225 
226  /* Initialize control segment. */
228  dsm_control->nitems = 0;
229  dsm_control->maxitems = maxitems;
230 }
static void dsm_postmaster_shutdown(int code, Datum arg)
Definition: dsm.c:358
#define PG_DYNSHMEM_CONTROL_MAGIC
Definition: dsm.c:50
static uint64 dsm_control_bytes_needed(uint32 nitems)
Definition: dsm.c:1255
#define PG_DYNSHMEM_SLOTS_PER_BACKEND
Definition: dsm.c:53
#define PG_DYNSHMEM_FIXED_SLOTS
Definition: dsm.c:52
static void dsm_cleanup_for_mmap(void)
Definition: dsm.c:320
int dynamic_shared_memory_type
Definition: dsm_impl.c:112
#define DSM_IMPL_MMAP
Definition: dsm_impl.h:20
int MaxBackends
Definition: globals.c:143
void on_shmem_exit(pg_on_exit_callback function, Datum arg)
Definition: ipc.c:365
static Datum PointerGetDatum(const void *X)
Definition: postgres.h:322
dsm_handle dsm_control
Definition: pg_shmem.h:36
uint32 magic
Definition: dsm.c:92

References Assert, DEBUG2, dsm_cleanup_for_mmap(), dsm_control, PGShmemHeader::dsm_control, dsm_control_bytes_needed(), dsm_control_handle, dsm_control_impl_private, dsm_control_mapped_size, DSM_HANDLE_INVALID, DSM_IMPL_MMAP, dsm_impl_op(), DSM_OP_CREATE, dsm_postmaster_shutdown(), dynamic_shared_memory_type, elog, ERROR, IsUnderPostmaster, dsm_control_header::magic, MaxBackends, dsm_control_header::maxitems, dsm_control_header::nitems, on_shmem_exit(), PG_DYNSHMEM_CONTROL_MAGIC, PG_DYNSHMEM_FIXED_SLOTS, PG_DYNSHMEM_SLOTS_PER_BACKEND, pg_global_prng_state, pg_prng_uint32(), and PointerGetDatum().

Referenced by CreateSharedMemoryAndSemaphores().

◆ dsm_segment_address()

◆ dsm_segment_handle()

◆ dsm_segment_map_length()

Size dsm_segment_map_length ( dsm_segment seg)

Definition at line 1105 of file dsm.c.

1106 {
1107  Assert(seg->mapped_address != NULL);
1108  return seg->mapped_size;
1109 }

References Assert, dsm_segment::mapped_address, and dsm_segment::mapped_size.

◆ dsm_shmem_init()

void dsm_shmem_init ( void  )

Definition at line 479 of file dsm.c.

480 {
481  size_t size = dsm_estimate_size();
482  bool found;
483 
484  if (size == 0)
485  return;
486 
487  dsm_main_space_begin = ShmemInitStruct("Preallocated DSM", size, &found);
488  if (!found)
489  {
491  size_t first_page = 0;
492  size_t pages;
493 
494  /* Reserve space for the FreePageManager. */
495  while (first_page * FPM_PAGE_SIZE < sizeof(FreePageManager))
496  ++first_page;
497 
498  /* Initialize it and give it all the rest of the space. */
500  pages = (size / FPM_PAGE_SIZE) - first_page;
501  FreePageManagerPut(fpm, first_page, pages);
502  }
503 }
size_t dsm_estimate_size(void)
Definition: dsm.c:470
void FreePageManagerInitialize(FreePageManager *fpm, char *base)
Definition: freepage.c:183
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:387

References dsm_estimate_size(), dsm_main_space_begin, FPM_PAGE_SIZE, FreePageManagerInitialize(), FreePageManagerPut(), ShmemInitStruct(), and size.

Referenced by CreateOrAttachShmemStructs().

◆ dsm_unpin_mapping()

void dsm_unpin_mapping ( dsm_segment seg)

Definition at line 934 of file dsm.c.

935 {
936  Assert(seg->resowner == NULL);
940 }
static void ResourceOwnerRememberDSM(ResourceOwner owner, dsm_segment *seg)
Definition: dsm.c:160
ResourceOwner CurrentResourceOwner
Definition: resowner.c:165
void ResourceOwnerEnlarge(ResourceOwner owner)
Definition: resowner.c:442

References Assert, CurrentResourceOwner, ResourceOwnerEnlarge(), ResourceOwnerRememberDSM(), and dsm_segment::resowner.

◆ dsm_unpin_segment()

void dsm_unpin_segment ( dsm_handle  handle)

Definition at line 988 of file dsm.c.

989 {
990  uint32 control_slot = INVALID_CONTROL_SLOT;
991  bool destroy = false;
992  uint32 i;
993 
994  /* Find the control slot for the given handle. */
995  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
996  for (i = 0; i < dsm_control->nitems; ++i)
997  {
998  /* Skip unused slots and segments that are concurrently going away. */
999  if (dsm_control->item[i].refcnt <= 1)
1000  continue;
1001 
1002  /* If we've found our handle, we can stop searching. */
1003  if (dsm_control->item[i].handle == handle)
1004  {
1005  control_slot = i;
1006  break;
1007  }
1008  }
1009 
1010  /*
1011  * We should definitely have found the slot, and it should not already be
1012  * in the process of going away, because this function should only be
1013  * called on a segment which is pinned.
1014  */
1015  if (control_slot == INVALID_CONTROL_SLOT)
1016  elog(ERROR, "cannot unpin unknown segment handle");
1017  if (!dsm_control->item[control_slot].pinned)
1018  elog(ERROR, "cannot unpin a segment that is not pinned");
1019  Assert(dsm_control->item[control_slot].refcnt > 1);
1020 
1021  /*
1022  * Allow implementation-specific code to run. We have to do this before
1023  * releasing the lock, because impl_private_pm_handle may get modified by
1024  * dsm_impl_unpin_segment.
1025  */
1026  if (!is_main_region_dsm_handle(handle))
1027  dsm_impl_unpin_segment(handle,
1028  &dsm_control->item[control_slot].impl_private_pm_handle);
1029 
1030  /* Note that 1 means no references (0 means unused slot). */
1031  if (--dsm_control->item[control_slot].refcnt == 1)
1032  destroy = true;
1033  dsm_control->item[control_slot].pinned = false;
1034 
1035  /* Now we can release the lock. */
1036  LWLockRelease(DynamicSharedMemoryControlLock);
1037 
1038  /* Clean up resources if that was the last reference. */
1039  if (destroy)
1040  {
1041  void *junk_impl_private = NULL;
1042  void *junk_mapped_address = NULL;
1043  Size junk_mapped_size = 0;
1044 
1045  /*
1046  * For an explanation of how error handling works in this case, see
1047  * comments in dsm_detach. Note that if we reach this point, the
1048  * current process certainly does not have the segment mapped, because
1049  * if it did, the reference count would have still been greater than 1
1050  * even after releasing the reference count held by the pin. The fact
1051  * that there can't be a dsm_segment for this handle makes it OK to
1052  * pass the mapped size, mapped address, and private data as NULL
1053  * here.
1054  */
1055  if (is_main_region_dsm_handle(handle) ||
1056  dsm_impl_op(DSM_OP_DESTROY, handle, 0, &junk_impl_private,
1057  &junk_mapped_address, &junk_mapped_size, WARNING))
1058  {
1059  LWLockAcquire(DynamicSharedMemoryControlLock, LW_EXCLUSIVE);
1060  if (is_main_region_dsm_handle(handle))
1062  dsm_control->item[control_slot].first_page,
1063  dsm_control->item[control_slot].npages);
1064  Assert(dsm_control->item[control_slot].handle == handle);
1065  Assert(dsm_control->item[control_slot].refcnt == 1);
1066  dsm_control->item[control_slot].refcnt = 0;
1067  LWLockRelease(DynamicSharedMemoryControlLock);
1068  }
1069  }
1070 }
void dsm_impl_unpin_segment(dsm_handle handle, void **impl_private)
Definition: dsm_impl.c:1014

References Assert, dsm_control, dsm_impl_op(), dsm_impl_unpin_segment(), dsm_main_space_begin, DSM_OP_DESTROY, elog, ERROR, dsm_control_item::first_page, FreePageManagerPut(), dsm_control_item::handle, i, dsm_control_item::impl_private_pm_handle, INVALID_CONTROL_SLOT, is_main_region_dsm_handle(), dsm_control_header::item, LW_EXCLUSIVE, LWLockAcquire(), LWLockRelease(), dsm_control_header::nitems, dsm_control_item::npages, dsm_control_item::pinned, dsm_control_item::refcnt, and WARNING.

Referenced by destroy_superblock(), and dsa_release_in_place().

◆ on_dsm_detach()

void on_dsm_detach ( dsm_segment seg,
on_dsm_detach_callback  function,
Datum  arg 
)

◆ reset_on_dsm_detach()

void reset_on_dsm_detach ( void  )

Definition at line 1170 of file dsm.c.

1171 {
1172  dlist_iter iter;
1173 
1175  {
1176  dsm_segment *seg = dlist_container(dsm_segment, node, iter.cur);
1177 
1178  /* Throw away explicit on-detach actions one by one. */
1179  while (!slist_is_empty(&seg->on_detach))
1180  {
1181  slist_node *node;
1183 
1184  node = slist_pop_head_node(&seg->on_detach);
1185  cb = slist_container(dsm_segment_detach_callback, node, node);
1186  pfree(cb);
1187  }
1188 
1189  /*
1190  * Decrementing the reference count is a sort of implicit on-detach
1191  * action; make sure we don't do that, either.
1192  */
1194  }
1195 }

References dsm_segment::control_slot, dlist_iter::cur, dlist_container, dlist_foreach, dsm_segment_list, INVALID_CONTROL_SLOT, dsm_segment::on_detach, pfree(), slist_container, slist_is_empty(), and slist_pop_head_node().

Referenced by on_exit_reset().