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Try accessing the access lists without locks by making the replacement process as atomic as possible.

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This commit is contained in:
Dirk Engling 2021-04-19 22:12:50 +02:00
parent 7c905ba729
commit fde79836e6
1 changed files with 7 additions and 7 deletions
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14
ot_accesslist.c
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@ -35,7 +35,7 @@ static int vector_compare_hash(const void *hash1, const void *hash2 ) {
/* Read initial access list */ /* Read initial access list */
static void accesslist_readfile( void ) { static void accesslist_readfile( void ) {
ot_hash *info_hash, *accesslist_new = NULL; ot_hash *info_hash, *accesslist_new = NULL, *accesslist_old;
char *map, *map_end, *read_offs; char *map, *map_end, *read_offs;
size_t maplen; size_t maplen;
@ -90,19 +90,19 @@ static void accesslist_readfile( void ) {
/* Now exchange the accesslist vector in the least race condition prone way */ /* Now exchange the accesslist vector in the least race condition prone way */
pthread_mutex_lock(&g_accesslist_mutex); pthread_mutex_lock(&g_accesslist_mutex);
free( g_accesslist );
g_accesslist = accesslist_new; accesslist_old = g_accesslist; /* Keep a copy for later free */
g_accesslist_size = info_hash - accesslist_new; g_accesslist_size = 0; /* Set size to 0 to prevent clients from searching through uninitialised memory */
g_accesslist = accesslist_new; /* Only now set a new list */
g_accesslist_size = info_hash - accesslist_new; /* And finally store it's size */
free(g_accesslist_old); /* If new list is active, the old one can be destroyed */
pthread_mutex_unlock(&g_accesslist_mutex); pthread_mutex_unlock(&g_accesslist_mutex);
} }
int accesslist_hashisvalid( ot_hash hash ) { int accesslist_hashisvalid( ot_hash hash ) {
void *exactmatch; void *exactmatch;
/* Lock should hardly ever be contended */
pthread_mutex_lock(&g_accesslist_mutex);
exactmatch = bsearch( hash, g_accesslist, g_accesslist_size, OT_HASH_COMPARE_SIZE, vector_compare_hash ); exactmatch = bsearch( hash, g_accesslist, g_accesslist_size, OT_HASH_COMPARE_SIZE, vector_compare_hash );
pthread_mutex_unlock(&g_accesslist_mutex);
#ifdef WANT_ACCESSLIST_BLACK #ifdef WANT_ACCESSLIST_BLACK
return exactmatch == NULL; return exactmatch == NULL;