Re: [PATCH net-next v1] net: fix sock compilation error under CONFIG_PREEMPT_RT

[Eric Dumazet]

On Sat, Feb 28, 2026 at 10:07 AM Jiayuan Chen <jiayuan.chen@xxxxxxxxx> wrote:
>
> From: Jiayuan Chen <jiayuan.chen@xxxxxxxxxx>
>
> 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()")
> Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxxx>
> ---
>  net/core/sock.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 9d841975a7a1..2461aba7b18a 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -3782,12 +3782,10 @@ 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;
> -
> -               tmp.slock = __SPIN_LOCK_UNLOCKED(tmp.slock);
> -               tmp.owned = 1;
> -               old.slock = __SPIN_LOCK_UNLOCKED(old.slock);
> -               old.owned = 0;
> +               socket_lock_t tmp = { .slock = __SPIN_LOCK_UNLOCKED(tmp.slock),
> +                                     .owned = 1 };
> +               socket_lock_t old = { .slock = __SPIN_LOCK_UNLOCKED(old.slock),
> +                                     .owned = 0 };
>                 if (likely(try_cmpxchg(&sk->sk_lock.combined,
>                                        &old.combined, tmp.combined)))
>                         return;

Thanks for your patch, could you please use a nicer formatting ?
(And keep an empty line between variables and code)

diff --git a/net/core/sock.c b/net/core/sock.c
index 9d841975a7a14a12769450a8d937af96f7777070..fba4d5b8553c58f700bda3dbd82ce68ec74187da
100644
--- 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;