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Commit1608902

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Preserve CurrentMemoryContext across notify and sinval interrupts.
ProcessIncomingNotify is called from the main processing loop thatnormally runs in MessageContext. That outer-loop code assumes thatwhatever it allocates will be cleaned up when we're done processingthe current client message --- but if we service a notify interrupt,then whatever gets allocated before the next switch intoMessageContext will be permanently leaked in TopMemoryContext,because CommitTransactionCommand sets CurrentMemoryContext toTopMemoryContext. There are observable leaks associated with(at least) encoding conversion of incoming queries and parametersattached to Bind messages.sinval catchup interrupts have a similar problem. There might beothers, but I've not identified any other clear cases.To fix, take care to save and restore CurrentMemoryContext acrossthe Start/CommitTransactionCommand calls in these functions.Per bug #18512 from wizardbrony. Commit to back branches only;in HEAD, this was dealt with by the riskier but more thoroughgoingapproach in commit1afe31f.Discussion:https://postgr.es/m/3478884.1718656625@sss.pgh.pa.us
1 parentf31c1e3 commit1608902

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2 files changed

+17
-1
lines changed

2 files changed

+17
-1
lines changed

‎src/backend/commands/async.c

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2250,6 +2250,8 @@ asyncQueueAdvanceTail(void)
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staticvoid
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ProcessIncomingNotify(boolflush)
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{
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MemoryContextoldcontext;
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/* We *must* reset the flag */
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notifyInterruptPending= false;
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@@ -2264,14 +2266,21 @@ ProcessIncomingNotify(bool flush)
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/*
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* We must run asyncQueueReadAllNotifications inside a transaction, else
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* bad things happen if it gets an error.
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* bad things happen if it gets an error. However, we need to preserve
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* the caller's memory context (typically MessageContext).
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*/
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oldcontext=CurrentMemoryContext;
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StartTransactionCommand();
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asyncQueueReadAllNotifications();
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CommitTransactionCommand();
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/* Caller's context had better not have been transaction-local */
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Assert(MemoryContextIsValid(oldcontext));
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MemoryContextSwitchTo(oldcontext);
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/*
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* If this isn't an end-of-command case, we must flush the notify messages
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* to ensure frontend gets them promptly.

‎src/backend/storage/ipc/sinval.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,7 @@
1717
#include"access/xact.h"
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#include"commands/async.h"
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#include"miscadmin.h"
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#include"nodes/memnodes.h"
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#include"storage/ipc.h"
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#include"storage/proc.h"
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#include"storage/sinvaladt.h"
@@ -184,6 +185,7 @@ ProcessCatchupInterrupt(void)
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* can just call AcceptInvalidationMessages() to do this. If we
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* aren't, we start and immediately end a transaction; the call to
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* AcceptInvalidationMessages() happens down inside transaction start.
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* Be sure to preserve caller's memory context when we do that.
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*
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* It is awfully tempting to just call AcceptInvalidationMessages()
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* without the rest of the xact start/stop overhead, and I think that
@@ -197,9 +199,14 @@ ProcessCatchupInterrupt(void)
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}
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else
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{
202+
MemoryContextoldcontext=CurrentMemoryContext;
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200204
elog(DEBUG4,"ProcessCatchupEvent outside transaction");
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StartTransactionCommand();
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CommitTransactionCommand();
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/* Caller's context had better not have been transaction-local */
208+
Assert(MemoryContextIsValid(oldcontext));
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MemoryContextSwitchTo(oldcontext);
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}
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}
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}

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