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- Use proper atomic operations to make the run time initialization

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controlled by svr_str_initialized be MP safe.
This commit is contained in:
John Baldwin 2001-01-23 21:07:16 +00:00
parent f843c385b1
commit 48f8ca448a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=71449
1 changed files with 20 additions and 10 deletions
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30
sys/compat/svr4/svr4_socket.c
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@ -84,17 +84,19 @@ svr4_find_socket(p, fp, dev, ino)
struct svr4_sockcache_entry *e;
void *cookie = ((struct socket *) fp->f_data)->so_emuldata;
if (!svr4_str_initialized) {
DPRINTF(("svr4_find_socket: uninitialized [%p,%d,%d]\n",
p, dev, ino));
TAILQ_INIT(&svr4_head);
svr4_str_initialized = 1;
if (svr4_str_initialized != 2) {
if (atomic_cmpset_acq_int(&svr4_str_initialized, 0, 1)) {
DPRINTF(("svr4_find_socket: uninitialized [%p,%d,%d]\n",
p, dev, ino));
TAILQ_INIT(&svr4_head);
atomic_store_rel(&svr4_str_initialized, 2);
}
return NULL;
}
DPRINTF(("svr4_find_socket: [%p,%d,%d]: ", p, dev, ino));
for (e = svr4_head.tqh_first; e != NULL; e = e->entries.tqe_next)
TAILQ_FOREACH(e, &svr4_head, entries)
if (e->p == p && e->dev == dev && e->ino == ino) {
#ifdef DIAGNOSTIC
if (e->cookie != NULL && e->cookie != cookie)
@ -123,10 +125,18 @@ svr4_add_socket(p, path, st)
struct svr4_sockcache_entry *e;
int len, error;
if (!svr4_str_initialized) {
TAILQ_INIT(&svr4_head);
svr4_str_initialized = 1;
}
/*
* Wait for the TAILQ to be initialized. Only the very first CPU
* will succeed on the atomic_cmpset(). The other CPU's will spin
* until the first one finishes the initialization. Once the
* initialization is complete, the condition will always fail
* avoiding expensive atomic operations in the common case.
*/
while (svr4_str_initialized != 2)
if (atomic_cmpset_acq_int(&svr4_str_initialized, 0, 1)) {
TAILQ_INIT(&svr4_head);
atomic_store_rel_int(&svr4_str_initialized, 2);
}
e = malloc(sizeof(*e), M_TEMP, M_WAITOK);
e->cookie = NULL;