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fix: remove pthread_mutex that causes self-deadlock on VLE queries #2433

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Merged
jrgemignani merged 1 commit into from
Jun 9, 2026
Merged

fix: remove pthread_mutex that causes self-deadlock on VLE queries #2433

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63 changes: 13 additions & 50 deletions src/backend/utils/adt/age_global_graph.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,6 @@
#include "catalog/ag_label.h"
#include "utils/ag_cache.h"

#include <pthread.h>

/* defines */
#define VERTEX_HTAB_NAME "Vertex to edge lists " /* added a space at end for */
Expand Down Expand Up @@ -152,18 +151,8 @@ typedef struct GRAPH_global_context
struct GRAPH_global_context *next; /* next graph */
} GRAPH_global_context;

/* container for GRAPH_global_context and its mutex */
typedef struct GRAPH_global_context_container
{
/* head of the list */
GRAPH_global_context *contexts;

/* mutex to protect the list */
pthread_mutex_t mutex_lock;
} GRAPH_global_context_container;

/* global variable to hold the per process GRAPH global contexts */
static GRAPH_global_context_container global_graph_contexts_container = {0};
static GRAPH_global_context *global_graph_contexts = NULL;

/*
* VertexEdgeArray helpers — flat-array adjacency container used by
Expand Down Expand Up @@ -1054,12 +1043,10 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
* 5) One or more other contexts do exist but, one or more are invalid.
*/

/* lock the global contexts list */
pthread_mutex_lock(&global_graph_contexts_container.mutex_lock);

/* free the invalidated GRAPH global contexts first */
prev_ggctx = NULL;
curr_ggctx = global_graph_contexts_container.contexts;
curr_ggctx = global_graph_contexts;
while (curr_ggctx != NULL)
{
GRAPH_global_context *next_ggctx = curr_ggctx->next;
Expand All @@ -1076,7 +1063,7 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
*/
if (prev_ggctx == NULL)
{
global_graph_contexts_container.contexts = next_ggctx;
global_graph_contexts = next_ggctx;
}
else
{
Expand All @@ -1089,8 +1076,6 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
/* if it wasn't successfull, there was a missing vertex entry */
if (!success)
{
/* unlock the mutex so we don't get a deadlock */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

ereport(ERROR, (errcode(ERRCODE_DATA_EXCEPTION),
errmsg("missing vertex or edge entry during free")));
Expand All @@ -1106,16 +1091,14 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
}

/* find our graph's context. if it exists, we are done */
curr_ggctx = global_graph_contexts_container.contexts;
curr_ggctx = global_graph_contexts;
while (curr_ggctx != NULL)
{
if (curr_ggctx->graph_oid == graph_oid)
{
/* switch our context back */
MemoryContextSwitchTo(oldctx);

/* we are done unlock the global contexts list */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

return curr_ggctx;
}
Expand All @@ -1125,17 +1108,17 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
/* otherwise, we need to create one and possibly attach it */
new_ggctx = palloc0(sizeof(GRAPH_global_context));

if (global_graph_contexts_container.contexts != NULL)
if (global_graph_contexts != NULL)
{
new_ggctx->next = global_graph_contexts_container.contexts;
new_ggctx->next = global_graph_contexts;
}
else
{
new_ggctx->next = NULL;
}

/* set the global context variable */
global_graph_contexts_container.contexts = new_ggctx;
global_graph_contexts = new_ggctx;
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/* set the graph name and oid */
new_ggctx->graph_name = pstrdup(graph_name);
Expand All @@ -1157,8 +1140,6 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
load_GRAPH_global_hashtables(new_ggctx);
freeze_GRAPH_global_hashtables(new_ggctx);

/* unlock the global contexts list */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

/* switch back to the previous memory context */
MemoryContextSwitchTo(oldctx);
Expand All @@ -1170,18 +1151,16 @@ GRAPH_global_context *manage_GRAPH_global_contexts(char *graph_name,
* Helper function to delete all of the global graph contexts used by the
* process. When done the global global_graph_contexts will be NULL.
*
* NOTE: Function uses a MUTEX global_graph_contexts_mutex
*
*/
static bool delete_GRAPH_global_contexts(void)
{
GRAPH_global_context *curr_ggctx = NULL;
bool retval = false;

/* lock contexts list */
pthread_mutex_lock(&global_graph_contexts_container.mutex_lock);

/* get the first context, if any */
curr_ggctx = global_graph_contexts_container.contexts;
curr_ggctx = global_graph_contexts;

/* free all GRAPH global contexts */
while (curr_ggctx != NULL)
Expand All @@ -1195,8 +1174,6 @@ static bool delete_GRAPH_global_contexts(void)
/* if it wasn't successfull, there was a missing vertex entry */
if (!success)
{
/* unlock the mutex so we don't get a deadlock */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

ereport(ERROR, (errcode(ERRCODE_DATA_EXCEPTION),
errmsg("missing vertex or edge entry during free")));
Expand All @@ -1209,10 +1186,8 @@ static bool delete_GRAPH_global_contexts(void)
}

/* reset the head of the contexts to NULL */
global_graph_contexts_container.contexts = NULL;
global_graph_contexts = NULL;

/* unlock the global contexts list */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

return retval;
}
Expand All @@ -1235,11 +1210,9 @@ static bool delete_specific_GRAPH_global_contexts(char *graph_name)
/* get the graph oid */
graph_oid = get_graph_oid(graph_name);

/* lock the global contexts list */
pthread_mutex_lock(&global_graph_contexts_container.mutex_lock);

/* get the first context, if any */
curr_ggctx = global_graph_contexts_container.contexts;
curr_ggctx = global_graph_contexts;

/* find the specified GRAPH global context */
while (curr_ggctx != NULL)
Expand All @@ -1256,7 +1229,7 @@ static bool delete_specific_GRAPH_global_contexts(char *graph_name)
*/
if (prev_ggctx == NULL)
{
global_graph_contexts_container.contexts = next_ggctx;
global_graph_contexts = next_ggctx;
}
else
{
Expand All @@ -1266,8 +1239,6 @@ static bool delete_specific_GRAPH_global_contexts(char *graph_name)
/* free the current graph context */
success = free_specific_GRAPH_global_context(curr_ggctx);

/* unlock the global contexts list */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

/* if it wasn't successfull, there was a missing vertex entry */
if (!success)
Expand All @@ -1285,8 +1256,6 @@ static bool delete_specific_GRAPH_global_contexts(char *graph_name)
curr_ggctx = next_ggctx;
}

/* unlock the global contexts list */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

/* we didn't find it, return false */
return false;
Expand Down Expand Up @@ -1347,19 +1316,15 @@ GRAPH_global_context *find_GRAPH_global_context(Oid graph_oid)
{
GRAPH_global_context *ggctx = NULL;

/* lock the global contexts lists */
pthread_mutex_lock(&global_graph_contexts_container.mutex_lock);

/* get the root */
ggctx = global_graph_contexts_container.contexts;
ggctx = global_graph_contexts;

while(ggctx != NULL)
{
/* if we found it return it */
if (ggctx->graph_oid == graph_oid)
{
/* unlock the global contexts lists */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

return ggctx;
}
Expand All @@ -1368,8 +1333,6 @@ GRAPH_global_context *find_GRAPH_global_context(Oid graph_oid)
ggctx = ggctx->next;
}

/* unlock the global contexts lists */
pthread_mutex_unlock(&global_graph_contexts_container.mutex_lock);

/* we did not find it so return NULL */
return NULL;
Expand Down
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