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

[Jiayuan Chen]

February 28, 2026 at 18:43, "Eric Dumazet" <edumazet@xxxxxxxxxx mailto:edumazet@xxxxxxxxxx?to=%22Eric%20Dumazet%22%20%3Cedumazet%40google.com%3E > wrote:


> 
> 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)

Ack. I will send it later. 

> 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;
>