Make res_init() thread safe.

res_init() was not atomic, which could give undesired behaviour. Now
res_init() is completely locked under one lock and the locking is
removed from __res_vinit().

Signed-off-by: Kenneth Soerensen <kenneth.sorensen@spectralink.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
index ae0dce5..f334d05 100644 (file)
--- a/libc/inet/resolv.c
+++ b/libc/inet/resolv.c
@@ -3426,6 +3426,7 @@ static void res_sync_func(void)
         */
 }
 
+/* has to be called under __resolv_lock */
 static int
 __res_vinit(res_state rp, int preinit)
 {
@@ -3434,7 +3435,6 @@ __res_vinit(res_state rp, int preinit)
        int m = 0;
 #endif
 
-       __UCLIBC_MUTEX_LOCK(__resolv_lock);
        __close_nameservers();
        __open_nameservers();
 
@@ -3526,7 +3526,6 @@ __res_vinit(res_state rp, int preinit)
 
        rp->options |= RES_INIT;
 
-       __UCLIBC_MUTEX_UNLOCK(__resolv_lock);
        return 0;
 }
 
@@ -3576,11 +3575,11 @@ res_init(void)
        if (!_res.id)
                _res.id = res_randomid();
 
-       __UCLIBC_MUTEX_UNLOCK(__resolv_lock);
-
        __res_vinit(&_res, 1);
        __res_sync = res_sync_func;
 
+       __UCLIBC_MUTEX_UNLOCK(__resolv_lock);
+
        return 0;
 }
 libc_hidden_def(res_init)
@@ -3679,7 +3678,11 @@ struct __res_state *__resp = &_res;
 int
 res_ninit(res_state statp)
 {
-       return __res_vinit(statp, 0);
+       int ret;
+       __UCLIBC_MUTEX_LOCK(__resolv_lock);
+       ret = __res_vinit(statp, 0);
+       __UCLIBC_MUTEX_UNLOCK(__resolv_lock);
+       return ret;
 }
 
 #endif /* L_res_init */