net: fix sock compilation error under CONFIG_PREEMPT_RT

When CONFIG_PREEMPT_RT is enabled, __SPIN_LOCK_UNLOCKED() expands to a
brace-enclosed initializer rather than a compound literal, which cannot
be used in assignment expressions. This causes a build failure:

  net/core/sock.c:3787:29: error: expected expression before '{' token
   3787 |                 tmp.slock = __SPIN_LOCK_UNLOCKED(tmp.slock);

Use declaration-with-initializer instead of assignment, consistent with
how __SPIN_LOCK_UNLOCKED() is used elsewhere in the kernel (e.g.
DEFINE_SPINLOCK).

Fixes: 5151ec54f586 ("net: use try_cmpxchg() in lock_sock_nested()")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260228111319.79506-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/sock.c b/net/core/sock.c
index 9d841975a7a14a12769450a8d937af96f7777070..fba4d5b8553c58f700bda3dbd82ce68ec74187da 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3782,12 +3782,15 @@ void noinline lock_sock_nested(struct sock *sk, int subclass)
        might_sleep();
 #ifdef CONFIG_64BIT
        if (sizeof(struct slock_owned) == sizeof(long)) {
-               socket_lock_t tmp, old;
+               socket_lock_t tmp = {
+                       .slock = __SPIN_LOCK_UNLOCKED(tmp.slock),
+                       .owned = 1,
+               };
+               socket_lock_t old = {
+                       .slock = __SPIN_LOCK_UNLOCKED(old.slock),
+                       .owned = 0,
+               };
 
-               tmp.slock = __SPIN_LOCK_UNLOCKED(tmp.slock);
-               tmp.owned = 1;
-               old.slock = __SPIN_LOCK_UNLOCKED(old.slock);
-               old.owned = 0;
                if (likely(try_cmpxchg(&sk->sk_lock.combined,
                                       &old.combined, tmp.combined)))
                        return;