#include "miscadmin.h"
#include "libpq/pqsignal.h"
#include "postmaster/bgworker_internals.h"
+#include "postmaster/postmaster.h"
#include "storage/barrier.h"
#include "storage/ipc.h"
#include "storage/latch.h"
typedef struct BackgroundWorkerSlot
{
bool in_use;
+ pid_t pid; /* InvalidPid = not started yet; 0 = dead */
+ uint64 generation; /* incremented when slot is recycled */
BackgroundWorker worker;
} BackgroundWorkerSlot;
BackgroundWorkerSlot slot[FLEXIBLE_ARRAY_MEMBER];
} BackgroundWorkerArray;
+struct BackgroundWorkerHandle
+{
+ int slot;
+ uint64 generation;
+};
+
BackgroundWorkerArray *BackgroundWorkerData;
/*
rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
Assert(slotno < max_worker_processes);
slot->in_use = true;
+ slot->pid = InvalidPid;
+ slot->generation = 0;
rw->rw_shmem_slot = slotno;
+ rw->rw_worker.bgw_notify_pid = 0; /* might be reinit after crash */
memcpy(&slot->worker, &rw->rw_worker, sizeof(BackgroundWorker));
++slotno;
}
slot->worker.bgw_function_name, BGW_MAXLEN);
/*
- * Copy remaining fields.
+ * Copy various fixed-size fields.
*
* flags, start_time, and restart_time are examined by the
* postmaster, but nothing too bad will happen if they are
rw->rw_worker.bgw_main = slot->worker.bgw_main;
rw->rw_worker.bgw_main_arg = slot->worker.bgw_main_arg;
+ /*
+ * Copy the PID to be notified about state changes, but only if
+ * the postmaster knows about a backend with that PID. It isn't
+ * an error if the postmaster doesn't know about the PID, because
+ * the backend that requested the worker could have died (or been
+ * killed) just after doing so. Nonetheless, at least until we get
+ * some experience with how this plays out in the wild, log a message
+ * at a relative high debug level.
+ */
+ rw->rw_worker.bgw_notify_pid = slot->worker.bgw_notify_pid;
+ if (!PostmasterMarkPIDForWorkerNotify(rw->rw_worker.bgw_notify_pid))
+ {
+ elog(DEBUG1, "worker notification PID %u is not valid",
+ rw->rw_worker.bgw_notify_pid);
+ rw->rw_worker.bgw_notify_pid = 0;
+ }
+
/* Initialize postmaster bookkeeping. */
rw->rw_backend = NULL;
rw->rw_pid = 0;
free(rw);
}
+/*
+ * Report the PID of a newly-launched background worker in shared memory.
+ *
+ * This function should only be called from the postmaster.
+ */
+void
+ReportBackgroundWorkerPID(RegisteredBgWorker *rw)
+{
+ BackgroundWorkerSlot *slot;
+
+ Assert(rw->rw_shmem_slot < max_worker_processes);
+ slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
+ slot->pid = rw->rw_pid;
+
+ if (rw->rw_worker.bgw_notify_pid != 0)
+ kill(rw->rw_worker.bgw_notify_pid, SIGUSR1);
+}
+
+/*
+ * Cancel SIGUSR1 notifications for a PID belonging to an exiting backend.
+ *
+ * This function should only be called from the postmaster.
+ */
+void
+BackgroundWorkerStopNotifications(pid_t pid)
+{
+ slist_iter siter;
+
+ slist_foreach(siter, &BackgroundWorkerList)
+ {
+ RegisteredBgWorker *rw;
+
+ rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
+ if (rw->rw_worker.bgw_notify_pid == pid)
+ rw->rw_worker.bgw_notify_pid = 0;
+ }
+}
+
#ifdef EXEC_BACKEND
/*
* In EXEC_BACKEND mode, workers use this to retrieve their details from
if (!SanityCheckBackgroundWorker(worker, LOG))
return;
+ if (worker->bgw_notify_pid != 0)
+ {
+ ereport(LOG,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("background worker \"%s\": only dynamic background workers can request notification",
+ worker->bgw_name)));
+ return;
+ }
+
/*
* Enforce maximum number of workers. Note this is overly restrictive: we
* could allow more non-shmem-connected workers, because these don't count
*
* Returns true on success and false on failure. Failure typically indicates
* that no background worker slots are currently available.
+ *
+ * If handle != NULL, we'll set *handle to a pointer that can subsequently
+ * be used as an argument to GetBackgroundWorkerPid(). The caller can
+ * free this pointer using pfree(), if desired.
*/
bool
-RegisterDynamicBackgroundWorker(BackgroundWorker *worker)
+RegisterDynamicBackgroundWorker(BackgroundWorker *worker,
+ BackgroundWorkerHandle **handle)
{
int slotno;
bool success = false;
+ uint64 generation;
/*
* We can't register dynamic background workers from the postmaster.
if (!slot->in_use)
{
memcpy(&slot->worker, worker, sizeof(BackgroundWorker));
+ slot->pid = InvalidPid; /* indicates not started yet */
+ slot->generation++;
+ generation = slot->generation;
/*
* Make sure postmaster doesn't see the slot as in use before
if (success)
SendPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE);
+ /*
+ * If we found a slot and the user has provided a handle, initialize it.
+ */
+ if (success && handle)
+ {
+ *handle = palloc(sizeof(BackgroundWorkerHandle));
+ (*handle)->slot = slotno;
+ (*handle)->generation = generation;
+ }
+
return success;
}
+
+/*
+ * Get the PID of a dynamically-registered background worker.
+ *
+ * If the worker is determined to be running, the return value will be
+ * BGWH_STARTED and *pidp will get the PID of the worker process.
+ * Otherwise, the return value will be BGWH_NOT_YET_STARTED if the worker
+ * hasn't been started yet, and BGWH_STOPPED if the worker was previously
+ * running but is no longer.
+ *
+ * In the latter case, the worker may be stopped temporarily (if it is
+ * configured for automatic restart, or if it exited with code 0) or gone
+ * for good (if it is configured not to restart and exited with code 1).
+ */
+BgwHandleStatus
+GetBackgroundWorkerPid(BackgroundWorkerHandle *handle, pid_t *pidp)
+{
+ BackgroundWorkerSlot *slot;
+ pid_t pid;
+
+ Assert(handle->slot < max_worker_processes);
+ slot = &BackgroundWorkerData->slot[handle->slot];
+
+ /*
+ * We could probably arrange to synchronize access to data using
+ * memory barriers only, but for now, let's just keep it simple and
+ * grab the lock. It seems unlikely that there will be enough traffic
+ * here to result in meaningful contention.
+ */
+ LWLockAcquire(BackgroundWorkerLock, LW_SHARED);
+
+ /*
+ * The generation number can't be concurrently changed while we hold the
+ * lock. The pid, which is updated by the postmaster, can change at any
+ * time, but we assume such changes are atomic. So the value we read
+ * won't be garbage, but it might be out of date by the time the caller
+ * examines it (but that's unavoidable anyway).
+ */
+ if (handle->generation != slot->generation)
+ pid = 0;
+ else
+ pid = slot->pid;
+
+ /* All done. */
+ LWLockRelease(BackgroundWorkerLock);
+
+ if (pid == 0)
+ return BGWH_STOPPED;
+ else if (pid == InvalidPid)
+ return BGWH_NOT_YET_STARTED;
+ *pidp = pid;
+ return BGWH_STARTED;
+}
+
+/*
+ * Wait for a background worker to start up.
+ *
+ * This is like GetBackgroundWorkerPid(), except that if the worker has not
+ * yet started, we wait for it to do so; thus, BGWH_NOT_YET_STARTED is never
+ * returned. However, if the postmaster has died, we give up and return
+ * BGWH_POSTMASTER_DIED, since it that case we know that startup will not
+ * take place.
+ */
+BgwHandleStatus
+WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
+{
+ BgwHandleStatus status;
+ pid_t pid;
+ int rc;
+ bool save_set_latch_on_sigusr1;
+
+ save_set_latch_on_sigusr1 = set_latch_on_sigusr1;
+ set_latch_on_sigusr1 = true;
+
+ PG_TRY();
+ {
+ for (;;)
+ {
+ CHECK_FOR_INTERRUPTS();
+
+ status = GetBackgroundWorkerPid(handle, &pid);
+ if (status != BGWH_NOT_YET_STARTED)
+ break;
+
+ rc = WaitLatch(&MyProc->procLatch,
+ WL_LATCH_SET | WL_POSTMASTER_DEATH, 0);
+
+ if (rc & WL_POSTMASTER_DEATH)
+ {
+ status = BGWH_POSTMASTER_DIED;
+ break;
+ }
+
+ ResetLatch(&MyProc->procLatch);
+ }
+ }
+ PG_CATCH();
+ {
+ set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
+ PG_RE_THROW();
+ }
+ PG_END_TRY();
+
+ set_latch_on_sigusr1 = save_set_latch_on_sigusr1;
+ *pidp = pid;
+ return status;
+}
projects / postgresql / blobdiff