[Tarantool-patches] [PATCH 3/7] txn: detach transaction from fiber.

[mechanik20051988]

From: mechanik20051988 <mechanik20.05.1988 at gmail.com>

Detach transaction from fiber: now it is possible to start
transaction in fiber, save the pointer to it in some place
independent from the fiber and then restore it other fiber.
For this purpose `fiber_on_stop` and `fiber_on_yield` triggers
was changed: previously they received pointer to transaction
from the fiber storage, now they receive it as their argument,
because fiber storage can be already empty when they called.
Also implement function `txn_detach`, which clear `fiber_on_stop`
and `fiber_on_yeild` triggers. Detached transaction does not
rollback in case when fiber stopped, but can be aborted in case
it does not support yeild.

Path of #5860
---
 src/box/txn.c | 29 ++++++++++++++++++++++-------
 src/box/txn.h | 11 +++++++++++
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/src/box/txn.c b/src/box/txn.c
index b80e722a4..de6a7f37d 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -302,8 +302,9 @@ txn_begin(void)
 	rlist_create(&txn->savepoints);
 	txn->fiber = NULL;
 	fiber_set_txn(fiber(), txn);
-	/* fiber_on_yield is initialized by engine on demand */
-	trigger_create(&txn->fiber_on_stop, txn_on_stop, NULL, NULL);
+	trigger_create(&txn->fiber_on_yield, txn_on_yield, txn, NULL);
+	trigger_create(&txn->fiber_on_stop, txn_on_stop, txn, NULL);
+	/* fiber_on_yield is added by engine on demand */
 	trigger_add(&fiber()->on_stop, &txn->fiber_on_stop);
 	/*
 	 * By default all transactions may yield.
@@ -1016,7 +1017,6 @@ txn_can_yield(struct txn *txn, bool set)
 		trigger_clear(&txn->fiber_on_yield);
 	} else if (!set && could) {
 		txn_clear_flags(txn, TXN_CAN_YIELD);
-		trigger_create(&txn->fiber_on_yield, txn_on_yield, NULL, NULL);
 		trigger_add(&fiber()->on_yield, &txn->fiber_on_yield);
 	}
 	return could;
@@ -1216,9 +1216,8 @@ txn_savepoint_release(struct txn_savepoint *svp)
 static int
 txn_on_stop(struct trigger *trigger, void *event)
 {
-	(void) trigger;
 	(void) event;
-	struct txn *txn = in_txn();
+	struct txn *txn = trigger->data;
 	assert(txn->signature == TXN_SIGNATURE_UNKNOWN);
 	txn->signature = TXN_SIGNATURE_ROLLBACK;
 	txn_rollback(txn);
@@ -1246,12 +1245,28 @@ txn_on_stop(struct trigger *trigger, void *event)
 static int
 txn_on_yield(struct trigger *trigger, void *event)
 {
-	(void) trigger;
 	(void) event;
-	struct txn *txn = in_txn();
+	struct txn *txn = trigger->data;
 	assert(txn != NULL);
 	assert(!txn_has_flag(txn, TXN_CAN_YIELD));
 	txn_rollback_to_svp(txn, NULL);
 	txn_set_flags(txn, TXN_IS_ABORTED_BY_YIELD);
 	return 0;
 }
+
+struct txn *
+txn_detach(void)
+{
+	struct txn *txn = in_txn();
+	if (txn == NULL)
+		return NULL;
+	if (!txn_has_flag(txn, TXN_CAN_YIELD)) {
+		struct trigger trigger;
+		trigger.data = txn;
+		txn_on_yield(&trigger, NULL);
+	}
+	trigger_clear(&txn->fiber_on_yield);
+	trigger_clear(&txn->fiber_on_stop);
+	fiber_set_txn(fiber(), NULL);
+	return txn;
+}
\ No newline at end of file
diff --git a/src/box/txn.h b/src/box/txn.h
index 8741dc6a1..b8bba67b8 100644
--- a/src/box/txn.h
+++ b/src/box/txn.h
@@ -457,6 +457,17 @@ fiber_set_txn(struct fiber *fiber, struct txn *txn)
 	fiber->storage.txn = txn;
 }
 
+/**
+ * Detach transaction from fiber.
+ * By default if the fiber is stopped the transaction
+ * started in this fiber is rollback. This function
+ * detaches transaction from fiber, leaving it alive
+ * after fiber is stopped.
+ * @pre txn == in_txn()
+ */
+struct txn *
+txn_detach(void);
+
 /**
  * Start a transaction explicitly.
  * @pre no transaction is active
-- 
2.20.1