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Fix possible crash due to incorrect allocation context.

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Commit af33039317 aimed to reduce
leakage from tqueue.c, which is good.  Unfortunately, by changing the
memory context in which all of gather_readnext() executes, it also
changed the context in which ExecShutdownGatherWorkers executes, which
is not good, because that function eventually causes a call to
ExecParallelRetrieveInstrumentation, which proceeds to allocate
planstate->worker_instrument in a short-lived context, causing a
crash.

Rushabh Lathia, reviewed by Amit Kapila and by me.
This commit is contained in:
Robert Haas 2016-08-16 13:23:32 -04:00
parent d95a7c3fbc
commit 0aa1e9a44d
1 changed files with 11 additions and 1 deletions
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12
src/backend/executor/execParallel.c
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@ -500,6 +500,7 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate,
int n;
int ibytes;
int plan_node_id = planstate->plan->plan_node_id;
MemoryContext oldcontext;
/* Find the instumentation for this node. */
for (i = 0; i < instrumentation->num_plan_nodes; ++i)
@ -514,10 +515,19 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate,
for (n = 0; n < instrumentation->num_workers; ++n)
InstrAggNode(planstate->instrument, &instrument[n]);
/* Also store the per-worker detail. */
/*
* Also store the per-worker detail.
*
* Worker instrumentation should be allocated in the same context as
* the regular instrumentation information, which is the per-query
* context. Switch into per-query memory context.
*/
oldcontext = MemoryContextSwitchTo(planstate->state->es_query_cxt);
ibytes = mul_size(instrumentation->num_workers, sizeof(Instrumentation));
planstate->worker_instrument =
palloc(ibytes + offsetof(WorkerInstrumentation, instrument));
MemoryContextSwitchTo(oldcontext);
planstate->worker_instrument->num_workers = instrumentation->num_workers;
memcpy(&planstate->worker_instrument->instrument, instrument, ibytes);