tcp: tcp_wfree() refactoring

Use try_cmpxchg() (instead of cmpxchg()) in a more readable way.

oval = smp_load_acquire(&sk->sk_tsq_flags);
do {
	...
} while (!try_cmpxchg(&sk->sk_tsq_flags, &oval, nval));

Reduce indentation level.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20221110190239.3531280-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d1cb1ec..894410d 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1139,6 +1139,8 @@ void tcp_wfree(struct sk_buff *skb)
        struct sock *sk = skb->sk;
        struct tcp_sock *tp = tcp_sk(sk);
        unsigned long flags, nval, oval;
+       struct tsq_tasklet *tsq;
+       bool empty;
 
        /* Keep one reference on sk_wmem_alloc.
         * Will be released by sk_free() from here or tcp_tasklet_func()
@@ -1155,28 +1157,23 @@ void tcp_wfree(struct sk_buff *skb)
        if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
                goto out;
 
-       for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) {
-               struct tsq_tasklet *tsq;
-               bool empty;
-
+       oval = smp_load_acquire(&sk->sk_tsq_flags);
+       do {
                if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED))
                        goto out;
 
                nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED;
-               nval = cmpxchg(&sk->sk_tsq_flags, oval, nval);
-               if (nval != oval)
-                       continue;
+       } while (!try_cmpxchg(&sk->sk_tsq_flags, &oval, nval));
 
-               /* queue this socket to tasklet queue */
-               local_irq_save(flags);
-               tsq = this_cpu_ptr(&tsq_tasklet);
-               empty = list_empty(&tsq->head);
-               list_add(&tp->tsq_node, &tsq->head);
-               if (empty)
-                       tasklet_schedule(&tsq->tasklet);
-               local_irq_restore(flags);
-               return;
-       }
+       /* queue this socket to tasklet queue */
+       local_irq_save(flags);
+       tsq = this_cpu_ptr(&tsq_tasklet);
+       empty = list_empty(&tsq->head);
+       list_add(&tp->tsq_node, &tsq->head);
+       if (empty)
+               tasklet_schedule(&tsq->tasklet);
+       local_irq_restore(flags);
+       return;
 out:
        sk_free(sk);
 }