PostgreSQL Source Code  git master
worker.c File Reference
#include "postgres.h"
#include "miscadmin.h"
#include "storage/ipc.h"
#include "storage/procarray.h"
#include "storage/shm_mq.h"
#include "storage/shm_toc.h"
#include "tcop/tcopprot.h"
#include "test_shm_mq.h"
Include dependency graph for worker.c:

Go to the source code of this file.

Functions

static void attach_to_queues (dsm_segment *seg, shm_toc *toc, int myworkernumber, shm_mq_handle **inqhp, shm_mq_handle **outqhp)
 
static void copy_messages (shm_mq_handle *inqh, shm_mq_handle *outqh)
 
void test_shm_mq_main (Datum main_arg)
 

Function Documentation

◆ attach_to_queues()

static void attach_to_queues ( dsm_segment seg,
shm_toc toc,
int  myworkernumber,
shm_mq_handle **  inqhp,
shm_mq_handle **  outqhp 
)
static

Definition at line 154 of file worker.c.

References MyProc, shm_mq_attach(), shm_mq_set_receiver(), shm_mq_set_sender(), and shm_toc_lookup().

Referenced by test_shm_mq_main().

156 {
157  shm_mq *inq;
158  shm_mq *outq;
159 
160  inq = shm_toc_lookup(toc, myworkernumber, false);
162  *inqhp = shm_mq_attach(inq, seg, NULL);
163  outq = shm_toc_lookup(toc, myworkernumber + 1, false);
164  shm_mq_set_sender(outq, MyProc);
165  *outqhp = shm_mq_attach(outq, seg, NULL);
166 }
PGPROC * MyProc
Definition: proc.c:67
void shm_mq_set_sender(shm_mq *mq, PGPROC *proc)
Definition: shm_mq.c:217
shm_mq_handle * shm_mq_attach(shm_mq *mq, dsm_segment *seg, BackgroundWorkerHandle *handle)
Definition: shm_mq.c:283
Definition: shm_mq.c:71
void shm_mq_set_receiver(shm_mq *mq, PGPROC *proc)
Definition: shm_mq.c:199
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232

◆ copy_messages()

static void copy_messages ( shm_mq_handle inqh,
shm_mq_handle outqh 
)
static

Definition at line 176 of file worker.c.

References CHECK_FOR_INTERRUPTS, shm_mq_receive(), shm_mq_send(), and SHM_MQ_SUCCESS.

Referenced by test_shm_mq_main().

177 {
178  Size len;
179  void *data;
180  shm_mq_result res;
181 
182  for (;;)
183  {
184  /* Notice any interrupts that have occurred. */
186 
187  /* Receive a message. */
188  res = shm_mq_receive(inqh, &len, &data, false);
189  if (res != SHM_MQ_SUCCESS)
190  break;
191 
192  /* Send it back out. */
193  res = shm_mq_send(outqh, len, data, false);
194  if (res != SHM_MQ_SUCCESS)
195  break;
196  }
197 }
shm_mq_result
Definition: shm_mq.h:36
size_t Size
Definition: c.h:528
shm_mq_result shm_mq_send(shm_mq_handle *mqh, Size nbytes, const void *data, bool nowait)
Definition: shm_mq.c:321
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:99
shm_mq_result shm_mq_receive(shm_mq_handle *mqh, Size *nbytesp, void **datap, bool nowait)
Definition: shm_mq.c:548

◆ test_shm_mq_main()

void test_shm_mq_main ( Datum  main_arg)

Definition at line 47 of file worker.c.

References attach_to_queues(), BackendPidGetProc(), BackgroundWorkerUnblockSignals(), BackgroundWorker::bgw_notify_pid, copy_messages(), DatumGetInt32, DEBUG1, die, dsm_attach(), dsm_detach(), dsm_segment_address(), elog, ereport, errcode(), errmsg(), ERROR, test_shm_mq_header::mutex, MyBgworkerEntry, PG_TEST_SHM_MQ_MAGIC, pqsignal(), proc_exit(), PGPROC::procLatch, SetLatch(), shm_toc_attach(), shm_toc_lookup(), SpinLockAcquire, SpinLockRelease, test_shm_mq_header::workers_attached, test_shm_mq_header::workers_ready, and test_shm_mq_header::workers_total.

48 {
49  dsm_segment *seg;
50  shm_toc *toc;
51  shm_mq_handle *inqh;
52  shm_mq_handle *outqh;
53  volatile test_shm_mq_header *hdr;
54  int myworkernumber;
55  PGPROC *registrant;
56 
57  /*
58  * Establish signal handlers.
59  *
60  * We want CHECK_FOR_INTERRUPTS() to kill off this worker process just as
61  * it would a normal user backend. To make that happen, we use die().
62  */
63  pqsignal(SIGTERM, die);
65 
66  /*
67  * Connect to the dynamic shared memory segment.
68  *
69  * The backend that registered this worker passed us the ID of a shared
70  * memory segment to which we must attach for further instructions. Once
71  * we've mapped the segment in our address space, attach to the table of
72  * contents so we can locate the various data structures we'll need to
73  * find within the segment.
74  *
75  * Note: at this point, we have not created any ResourceOwner in this
76  * process. This will result in our DSM mapping surviving until process
77  * exit, which is fine. If there were a ResourceOwner, it would acquire
78  * ownership of the mapping, but we have no need for that.
79  */
80  seg = dsm_attach(DatumGetInt32(main_arg));
81  if (seg == NULL)
82  ereport(ERROR,
83  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
84  errmsg("unable to map dynamic shared memory segment")));
86  if (toc == NULL)
87  ereport(ERROR,
88  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
89  errmsg("bad magic number in dynamic shared memory segment")));
90 
91  /*
92  * Acquire a worker number.
93  *
94  * By convention, the process registering this background worker should
95  * have stored the control structure at key 0. We look up that key to
96  * find it. Our worker number gives our identity: there may be just one
97  * worker involved in this parallel operation, or there may be many.
98  */
99  hdr = shm_toc_lookup(toc, 0, false);
100  SpinLockAcquire(&hdr->mutex);
101  myworkernumber = ++hdr->workers_attached;
102  SpinLockRelease(&hdr->mutex);
103  if (myworkernumber > hdr->workers_total)
104  ereport(ERROR,
105  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
106  errmsg("too many message queue testing workers already")));
107 
108  /*
109  * Attach to the appropriate message queues.
110  */
111  attach_to_queues(seg, toc, myworkernumber, &inqh, &outqh);
112 
113  /*
114  * Indicate that we're fully initialized and ready to begin the main part
115  * of the parallel operation.
116  *
117  * Once we signal that we're ready, the user backend is entitled to assume
118  * that our on_dsm_detach callbacks will fire before we disconnect from
119  * the shared memory segment and exit. Generally, that means we must have
120  * attached to all relevant dynamic shared memory data structures by now.
121  */
122  SpinLockAcquire(&hdr->mutex);
123  ++hdr->workers_ready;
124  SpinLockRelease(&hdr->mutex);
126  if (registrant == NULL)
127  {
128  elog(DEBUG1, "registrant backend has exited prematurely");
129  proc_exit(1);
130  }
131  SetLatch(&registrant->procLatch);
132 
133  /* Do the work. */
134  copy_messages(inqh, outqh);
135 
136  /*
137  * We're done. For cleanliness, explicitly detach from the shared memory
138  * segment (that would happen anyway during process exit, though).
139  */
140  dsm_detach(seg);
141  proc_exit(1);
142 }
#define DEBUG1
Definition: elog.h:25
#define DatumGetInt32(X)
Definition: postgres.h:472
PGPROC * BackendPidGetProc(int pid)
Definition: procarray.c:3036
dsm_segment * dsm_attach(dsm_handle h)
Definition: dsm.c:631
void proc_exit(int code)
Definition: ipc.c:104
int errcode(int sqlerrcode)
Definition: elog.c:691
BackgroundWorker * MyBgworkerEntry
Definition: postmaster.c:194
void SetLatch(Latch *latch)
Definition: latch.c:505
Latch procLatch
Definition: proc.h:129
#define SpinLockAcquire(lock)
Definition: spin.h:62
#define ERROR
Definition: elog.h:43
static void copy_messages(shm_mq_handle *inqh, shm_mq_handle *outqh)
Definition: worker.c:176
#define SpinLockRelease(lock)
Definition: spin.h:64
shm_toc * shm_toc_attach(uint64 magic, void *address)
Definition: shm_toc.c:64
#define ereport(elevel,...)
Definition: elog.h:155
pqsigfunc pqsignal(int signum, pqsigfunc handler)
Definition: signal.c:170
void * dsm_segment_address(dsm_segment *seg)
Definition: dsm.c:1054
void dsm_detach(dsm_segment *seg)
Definition: dsm.c:769
int errmsg(const char *fmt,...)
Definition: elog.c:902
pid_t bgw_notify_pid
Definition: bgworker.h:99
#define elog(elevel,...)
Definition: elog.h:228
Definition: proc.h:120
static void attach_to_queues(dsm_segment *seg, shm_toc *toc, int myworkernumber, shm_mq_handle **inqhp, shm_mq_handle **outqhp)
Definition: worker.c:154
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232
#define die(msg)
Definition: pg_test_fsync.c:97
#define PG_TEST_SHM_MQ_MAGIC
Definition: test_shm_mq.h:22
void BackgroundWorkerUnblockSignals(void)
Definition: postmaster.c:5735