postgresql/contrib/test_shm_mq/setup.c

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/*--------------------------------------------------------------------------
*
* setup.c
* Code to set up a dynamic shared memory segments and a specified
* number of background workers for shared memory message queue
* testing.
*
* Copyright (C) 2013, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/test_shm_mq/setup.c
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "miscadmin.h"
#include "postmaster/bgworker.h"
#include "storage/procsignal.h"
#include "storage/shm_toc.h"
#include "utils/memutils.h"
#include "test_shm_mq.h"
typedef struct
{
int nworkers;
BackgroundWorkerHandle *handle[FLEXIBLE_ARRAY_MEMBER];
} worker_state;
static void setup_dynamic_shared_memory(int64 queue_size, int nworkers,
dsm_segment **segp,
test_shm_mq_header **hdrp,
shm_mq **outp, shm_mq **inp);
static worker_state *setup_background_workers(int nworkers,
dsm_segment *seg);
static void cleanup_background_workers(dsm_segment *seg, Datum arg);
static void wait_for_workers_to_become_ready(worker_state *wstate,
volatile test_shm_mq_header *hdr);
static bool check_worker_status(worker_state *wstate);
/*
* Set up a dynamic shared memory segment and zero or more background workers
* for a test run.
*/
void
test_shm_mq_setup(int64 queue_size, int32 nworkers, dsm_segment **segp,
shm_mq_handle **output, shm_mq_handle **input)
{
dsm_segment *seg;
test_shm_mq_header *hdr;
shm_mq *outq = NULL; /* placate compiler */
shm_mq *inq = NULL; /* placate compiler */
worker_state *wstate;
/* Set up a dynamic shared memory segment. */
setup_dynamic_shared_memory(queue_size, nworkers, &seg, &hdr, &outq, &inq);
*segp = seg;
/* Register background workers. */
wstate = setup_background_workers(nworkers, seg);
/* Attach the queues. */
*output = shm_mq_attach(outq, seg, wstate->handle[0]);
*input = shm_mq_attach(inq, seg, wstate->handle[nworkers - 1]);
/* Wait for workers to become ready. */
wait_for_workers_to_become_ready(wstate, hdr);
/*
* Once we reach this point, all workers are ready. We no longer need
* to kill them if we die; they'll die on their own as the message queues
* shut down.
*/
cancel_on_dsm_detach(seg, cleanup_background_workers,
PointerGetDatum(wstate));
pfree(wstate);
}
/*
* Set up a dynamic shared memory segment.
*
* We set up a small control region that contains only a test_shm_mq_header,
* plus one region per message queue. There are as many message queues as
* the number of workers, plus one.
*/
static void
setup_dynamic_shared_memory(int64 queue_size, int nworkers,
dsm_segment **segp, test_shm_mq_header **hdrp,
shm_mq **outp, shm_mq **inp)
{
shm_toc_estimator e;
int i;
uint64 segsize;
dsm_segment *seg;
shm_toc *toc;
test_shm_mq_header *hdr;
/* Ensure a valid queue size. */
if (queue_size < 0 || ((uint64) queue_size) < shm_mq_minimum_size)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("queue size must be at least %lu bytes",
(unsigned long) shm_mq_minimum_size)));
/*
* Estimate how much shared memory we need.
*
* Because the TOC machinery may choose to insert padding of oddly-sized
* requests, we must estimate each chunk separately.
*
* We need one key to register the location of the header, and we need
* nworkers + 1 keys to track the locations of the message queues.
*/
shm_toc_initialize_estimator(&e);
shm_toc_estimate_chunk(&e, sizeof(test_shm_mq_header));
for (i = 0; i <= nworkers; ++i)
shm_toc_estimate_chunk(&e, queue_size);
shm_toc_estimate_keys(&e, 2 + nworkers);
segsize = shm_toc_estimate(&e);
/* Create the shared memory segment and establish a table of contents. */
seg = dsm_create(shm_toc_estimate(&e));
toc = shm_toc_create(PG_TEST_SHM_MQ_MAGIC, dsm_segment_address(seg),
segsize);
/* Set up the header region. */
hdr = shm_toc_allocate(toc, sizeof(test_shm_mq_header));
SpinLockInit(&hdr->mutex);
hdr->workers_total = nworkers;
hdr->workers_attached = 0;
hdr->workers_ready = 0;
shm_toc_insert(toc, 0, hdr);
/* Set up one message queue per worker, plus one. */
for (i = 0; i <= nworkers; ++i)
{
shm_mq *mq;
mq = shm_mq_create(shm_toc_allocate(toc, queue_size), queue_size);
shm_toc_insert(toc, i + 1, mq);
if (i == 0)
{
/* We send messages to the first queue. */
shm_mq_set_sender(mq, MyProc);
*outp = mq;
}
if (i == nworkers)
{
/* We receive messages from the last queue. */
shm_mq_set_receiver(mq, MyProc);
*inp = mq;
}
}
/* Return results to caller. */
*segp = seg;
*hdrp = hdr;
}
/*
* Register background workers.
*/
static worker_state *
setup_background_workers(int nworkers, dsm_segment *seg)
{
MemoryContext oldcontext;
BackgroundWorker worker;
worker_state *wstate;
int i;
/*
* We need the worker_state object and the background worker handles to
* which it points to be allocated in CurTransactionContext rather than
* ExprContext; otherwise, they'll be destroyed before the on_dsm_detach
* hooks run.
*/
oldcontext = MemoryContextSwitchTo(CurTransactionContext);
/* Create worker state object. */
wstate = MemoryContextAlloc(TopTransactionContext,
offsetof(worker_state, handle) +
sizeof(BackgroundWorkerHandle *) * nworkers);
wstate->nworkers = 0;
/*
* Arrange to kill all the workers if we abort before all workers are
* finished hooking themselves up to the dynamic shared memory segment.
*
* If we die after all the workers have finished hooking themselves up
* to the dynamic shared memory segment, we'll mark the two queues to
* which we're directly connected as detached, and the worker(s)
* connected to those queues will exit, marking any other queues to
* which they are connected as detached. This will cause any
* as-yet-unaware workers connected to those queues to exit in their
* turn, and so on, until everybody exits.
*
* But suppose the workers which are supposed to connect to the queues
* to which we're directly attached exit due to some error before they
* actually attach the queues. The remaining workers will have no way of
* knowing this. From their perspective, they're still waiting for those
* workers to start, when in fact they've already died.
*/
on_dsm_detach(seg, cleanup_background_workers,
PointerGetDatum(wstate));
/* Configure a worker. */
worker.bgw_flags = BGWORKER_SHMEM_ACCESS;
worker.bgw_start_time = BgWorkerStart_ConsistentState;
worker.bgw_restart_time = BGW_NEVER_RESTART;
worker.bgw_main = NULL; /* new worker might not have library loaded */
sprintf(worker.bgw_library_name, "test_shm_mq");
sprintf(worker.bgw_function_name, "test_shm_mq_main");
snprintf(worker.bgw_name, BGW_MAXLEN, "test_shm_mq");
worker.bgw_main_arg = UInt32GetDatum(dsm_segment_handle(seg));
/* set bgw_notify_pid, so we can detect if the worker stops */
worker.bgw_notify_pid = MyProcPid;
/* Register the workers. */
for (i = 0; i < nworkers; ++i)
{
if (!RegisterDynamicBackgroundWorker(&worker, &wstate->handle[i]))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
errmsg("could not register background process"),
errhint("You may need to increase max_worker_processes.")));
++wstate->nworkers;
}
/* All done. */
MemoryContextSwitchTo(oldcontext);
return wstate;
}
static void
cleanup_background_workers(dsm_segment *seg, Datum arg)
{
worker_state *wstate = (worker_state *) DatumGetPointer(arg);
while (wstate->nworkers > 0)
{
--wstate->nworkers;
TerminateBackgroundWorker(wstate->handle[wstate->nworkers]);
}
}
static void
wait_for_workers_to_become_ready(worker_state *wstate,
volatile test_shm_mq_header *hdr)
{
bool save_set_latch_on_sigusr1;
bool result = false;
save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
set_latch_on_sigusr1 = true;
PG_TRY();
{
for (;;)
{
int workers_ready;
/* If all the workers are ready, we have succeeded. */
SpinLockAcquire(&hdr->mutex);
workers_ready = hdr->workers_ready;
SpinLockRelease(&hdr->mutex);
if (workers_ready >= wstate->nworkers)
{
result = true;
break;
}
/* If any workers (or the postmaster) have died, we have failed. */
if (!check_worker_status(wstate))
{
result = false;
break;
}
/* Wait to be signalled. */
WaitLatch(&MyProc->procLatch, WL_LATCH_SET, 0);
/* An interrupt may have occurred while we were waiting. */
CHECK_FOR_INTERRUPTS();
/* Reset the latch so we don't spin. */
ResetLatch(&MyProc->procLatch);
}
}
PG_CATCH();
{
set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
PG_RE_THROW();
}
PG_END_TRY();
if (!result)
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
errmsg("one or more background workers failed to start")));
}
static bool
check_worker_status(worker_state *wstate)
{
int n;
/* If any workers (or the postmaster) have died, we have failed. */
for (n = 0; n < wstate->nworkers; ++n)
{
BgwHandleStatus status;
pid_t pid;
status = GetBackgroundWorkerPid(wstate->handle[n], &pid);
if (status == BGWH_STOPPED || status == BGWH_POSTMASTER_DIED)
return false;
}
/* Otherwise, things still look OK. */
return true;
}