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Fix thread contention in string-cache #441

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merged 1 commit into from
Dec 10, 2024
Merged

Fix thread contention in string-cache #441

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12 changes: 10 additions & 2 deletions string-cache.c
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ typedef struct
} StringCacheEntry;

static GHashTable *string_cache = NULL;
static pthread_mutex_t string_cache_lock = PTHREAD_MUTEX_INITIALIZER;

/* Function to create a new cache entry. */
static StringCacheEntry *
Expand Down Expand Up @@ -68,19 +69,20 @@ string_cache_get (const char *str)
return NULL;
}

pthread_mutex_lock (&string_cache_lock);
StringCacheEntry *entry = g_hash_table_lookup (string_cache, str);
if (entry)
{
entry->refcount++;
return entry->str;
}
else
{
entry = string_cache_entry_new (str);
/* Use entry->str as the key to ensure hash/equal functions operate on the string */
g_hash_table_insert (string_cache, entry->str, entry);
return entry->str;
}
pthread_mutex_unlock (&string_cache_lock);
return entry->str;
}

/* Decrease the reference count of a string and remove it if refcount reaches 0 */
Expand All @@ -92,6 +94,7 @@ string_cache_release (const char *str)
return;
}

pthread_mutex_lock (&string_cache_lock);
StringCacheEntry *entry = g_hash_table_lookup (string_cache, str);
if (entry)
{
Expand All @@ -101,6 +104,7 @@ string_cache_release (const char *str)
g_hash_table_remove (string_cache, str);
}
}
pthread_mutex_unlock (&string_cache_lock);
}

/* Amount of actual memory used to store this string */
Expand Down Expand Up @@ -128,18 +132,22 @@ string_cache_memuse (const char *str, bool pss)
void
string_cache_init ()
{
pthread_mutex_lock (&string_cache_lock);
if (!string_cache)
{
string_cache =
g_hash_table_new_full (g_str_hash, g_str_equal, NULL,
(GDestroyNotify) string_cache_entry_free);
}
pthread_mutex_unlock (&string_cache_lock);
}

/* This function should only be called when *all* strings have been released. */
void
string_cache_deinit ()
{
pthread_mutex_lock (&string_cache_lock);
g_hash_table_destroy (string_cache);
string_cache = NULL;
pthread_mutex_unlock (&string_cache_lock);
}
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