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Fix and enhance the assertion of no palloc's in a critical section.

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The assertion failed if WAL_DEBUG or LWLOCK_STATS was enabled; fix that by
using separate memory contexts for the allocations made within those code
blocks.

This patch introduces a mechanism for marking any memory context as allowed
in a critical section. Previously ErrorContext was exempt as a special case.

Instead of a blanket exception of the checkpointer process, only exempt the
memory context used for the pending ops hash table.
This commit is contained in:
Heikki Linnakangas
2014-06-30 10:13:48 +03:00
parent a749a23d7a
commit 1c6821be31
9 changed files with 147 additions and 42 deletions
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25
src/backend/storage/smgr/md.c
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@@ -115,7 +115,7 @@ typedef struct _MdfdVec
struct _MdfdVec *mdfd_chain; /* next segment, or NULL */
} MdfdVec;
static MemoryContext MdCxt; /* context for all md.c allocations */
static MemoryContext MdCxt; /* context for all MdfdVec objects */
/*
@@ -157,6 +157,7 @@ typedef struct
static HTAB *pendingOpsTable = NULL;
static List *pendingUnlinks = NIL;
static MemoryContext pendingOpsCxt; /* context for the above */
static CycleCtr mdsync_cycle_ctr = 0;
static CycleCtr mdckpt_cycle_ctr = 0;
@@ -209,11 +210,27 @@ mdinit(void)
{
HASHCTL hash_ctl;
/*
* XXX: The checkpointer needs to add entries to the pending ops table
* when absorbing fsync requests. That is done within a critical
* section, which isn't usually allowed, but we make an exception.
* It means that there's a theoretical possibility that you run out of
* memory while absorbing fsync requests, which leads to a PANIC.
* Fortunately the hash table is small so that's unlikely to happen in
* practice.
*/
pendingOpsCxt = AllocSetContextCreate(MdCxt,
"Pending Ops Context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
MemoryContextAllowInCriticalSection(pendingOpsCxt, true);
MemSet(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = sizeof(RelFileNode);
hash_ctl.entrysize = sizeof(PendingOperationEntry);
hash_ctl.hash = tag_hash;
hash_ctl.hcxt = MdCxt;
hash_ctl.hcxt = pendingOpsCxt;
pendingOpsTable = hash_create("Pending Ops Table",
100L,
&hash_ctl,
@@ -1516,7 +1533,7 @@ RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
else if (segno == UNLINK_RELATION_REQUEST)
{
/* Unlink request: put it in the linked list */
MemoryContext oldcxt = MemoryContextSwitchTo(MdCxt);
MemoryContext oldcxt = MemoryContextSwitchTo(pendingOpsCxt);
PendingUnlinkEntry *entry;
/* PendingUnlinkEntry doesn't store forknum, since it's always MAIN */
@@ -1533,7 +1550,7 @@ RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
else
{
/* Normal case: enter a request to fsync this segment */
MemoryContext oldcxt = MemoryContextSwitchTo(MdCxt);
MemoryContext oldcxt = MemoryContextSwitchTo(pendingOpsCxt);
PendingOperationEntry *entry;
bool found;