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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.

156{
157 shm_mq *inq;
158 shm_mq *outq;
159
160 inq = shm_toc_lookup(toc, myworkernumber, false);
161 shm_mq_set_receiver(inq, MyProc);
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}
shm_mq_set_sender
void shm_mq_set_sender(shm_mq *mq, PGPROC *proc)
Definition: shm_mq.c:224
shm_mq_set_receiver
void shm_mq_set_receiver(shm_mq *mq, PGPROC *proc)
Definition: shm_mq.c:206
shm_mq_attach
shm_mq_handle * shm_mq_attach(shm_mq *mq, dsm_segment *seg, BackgroundWorkerHandle *handle)
Definition: shm_mq.c:290
shm_toc_lookup
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232
MyProc
PGPROC * MyProc
Definition: proc.c:66
shm_mq
Definition: shm_mq.c:72

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

Referenced by test_shm_mq_main().

◆ copy_messages()

static void copy_messages ( shm_mq_handle *  inqh,
shm_mq_handle *  outqh 
)
static

Definition at line 176 of file worker.c.

177{
178 Size len;
179 void *data;
180 shm_mq_result res;
181
182 for (;;)
183 {
184 /* Notice any interrupts that have occurred. */
185 CHECK_FOR_INTERRUPTS();
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, true);
194 if (res != SHM_MQ_SUCCESS)
195 break;
196 }
197}
Size
size_t Size
Definition: c.h:576
CHECK_FOR_INTERRUPTS
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:122
len
const void size_t len
Definition: pg_crc32c_sse42.c:25
data
const void * data
Definition: pg_crc32c_sse42.c:24
shm_mq_receive
shm_mq_result shm_mq_receive(shm_mq_handle *mqh, Size *nbytesp, void **datap, bool nowait)
Definition: shm_mq.c:572
shm_mq_send
shm_mq_result shm_mq_send(shm_mq_handle *mqh, Size nbytes, const void *data, bool nowait, bool force_flush)
Definition: shm_mq.c:329
shm_mq_result
shm_mq_result
Definition: shm_mq.h:37
SHM_MQ_SUCCESS
@ SHM_MQ_SUCCESS
Definition: shm_mq.h:38

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

Referenced by test_shm_mq_main().

◆ test_shm_mq_main()

void test_shm_mq_main ( Datum  main_arg)

Definition at line 47 of file worker.c.

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);
64 BackgroundWorkerUnblockSignals();
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")));
85 toc = shm_toc_attach(PG_TEST_SHM_MQ_MAGIC, dsm_segment_address(seg));
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);
125 registrant = BackendPidGetProc(MyBgworkerEntry->bgw_notify_pid);
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}
BackgroundWorkerUnblockSignals
void BackgroundWorkerUnblockSignals(void)
Definition: bgworker.c:926
dsm_detach
void dsm_detach(dsm_segment *seg)
Definition: dsm.c:803
dsm_segment_address
void * dsm_segment_address(dsm_segment *seg)
Definition: dsm.c:1095
dsm_attach
dsm_segment * dsm_attach(dsm_handle h)
Definition: dsm.c:665
errcode
int errcode(int sqlerrcode)
Definition: elog.c:853
errmsg
int errmsg(const char *fmt,...)
Definition: elog.c:1070
DEBUG1
#define DEBUG1
Definition: elog.h:30
ERROR
#define ERROR
Definition: elog.h:39
elog
#define elog(elevel,...)
Definition: elog.h:225
ereport
#define ereport(elevel,...)
Definition: elog.h:149
proc_exit
void proc_exit(int code)
Definition: ipc.c:104
SetLatch
void SetLatch(Latch *latch)
Definition: latch.c:288
die
#define die(msg)
Definition: pg_test_fsync.c:100
pqsignal
#define pqsignal
Definition: port.h:521
DatumGetInt32
static int32 DatumGetInt32(Datum X)
Definition: postgres.h:207
MyBgworkerEntry
BackgroundWorker * MyBgworkerEntry
Definition: postmaster.c:196
BackendPidGetProc
PGPROC * BackendPidGetProc(int pid)
Definition: procarray.c:3196
shm_toc_attach
shm_toc * shm_toc_attach(uint64 magic, void *address)
Definition: shm_toc.c:64
SpinLockRelease
#define SpinLockRelease(lock)
Definition: spin.h:61
SpinLockAcquire
#define SpinLockAcquire(lock)
Definition: spin.h:59
BackgroundWorker::bgw_notify_pid
pid_t bgw_notify_pid
Definition: bgworker.h:100
PGPROC
Definition: proc.h:163
PGPROC::procLatch
Latch procLatch
Definition: proc.h:170
dsm_segment
Definition: dsm.c:67
shm_mq_handle
Definition: shm_mq.c:138
shm_toc
Definition: shm_toc.c:27
test_shm_mq_header
Definition: test_shm_mq.h:30
test_shm_mq_header::workers_total
int workers_total
Definition: test_shm_mq.h:32
test_shm_mq_header::mutex
slock_t mutex
Definition: test_shm_mq.h:31
test_shm_mq_header::workers_attached
int workers_attached
Definition: test_shm_mq.h:33
test_shm_mq_header::workers_ready
int workers_ready
Definition: test_shm_mq.h:34
attach_to_queues
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
copy_messages
static void copy_messages(shm_mq_handle *inqh, shm_mq_handle *outqh)
Definition: worker.c:176
PG_TEST_SHM_MQ_MAGIC
#define PG_TEST_SHM_MQ_MAGIC
Definition: test_shm_mq.h:22

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.