pppx(4): kill useless rwlock `pppx_ifs_lk'

[Vitaliy Makkoveev]

`pppx_ifs_lk' used to protect `pppx_ifs' tree, But this tree is accessed
under KERNL_LOCK() and there is no concurency. Also we don't sleep while
holding this lock. So it's useless, kill it for simplification.

Index: sys/net/if_pppx.c
===================================================================
RCS file: /cvs/src/sys/net/if_pppx.c,v
retrieving revision 1.84
diff -u -p -r1.84 if_pppx.c
--- sys/net/if_pppx.c   18 Apr 2020 04:03:56 -0000      1.84
+++ sys/net/if_pppx.c   25 May 2020 08:31:20 -0000
@@ -165,7 +165,6 @@ pppx_if_cmp(const struct pppx_if *a, con
        return memcmp(&a->pxi_key, &b->pxi_key, sizeof(a->pxi_key));
 }
 
-struct rwlock                  pppx_ifs_lk = RWLOCK_INITIALIZER("pppxifs");
 RBT_HEAD(pppx_ifs, pppx_if)    pppx_ifs = RBT_INITIALIZER(&pppx_ifs);
 RBT_PROTOTYPE(pppx_ifs, pppx_if, pxi_entry, pppx_if_cmp);
 
@@ -620,8 +619,6 @@ pppx_if_next_unit(void)
        struct pppx_if *pxi;
        int unit = 0;
 
-       rw_assert_wrlock(&pppx_ifs_lk);
-
        /* this is safe without splnet since we're not modifying it */
        do {
                int found = 0;
@@ -650,11 +647,9 @@ pppx_if_find(struct pppx_dev *pxd, int s
        key.pxik_session_id = session_id;
        key.pxik_protocol = protocol;
 
-       rw_enter_read(&pppx_ifs_lk);
        pxi = RBT_FIND(pppx_ifs, &pppx_ifs, (struct pppx_if *)&key);
        if (pxi && pxi->pxi_ready == 0)
                pxi = NULL;
-       rw_exit_read(&pppx_ifs_lk);
 
        return pxi;
 }
@@ -828,12 +823,10 @@ pppx_add_session(struct pppx_dev *pxd, s
 #endif
 
        /* try to set the interface up */
-       rw_enter_write(&pppx_ifs_lk);
        unit = pppx_if_next_unit();
        if (unit < 0) {
                pool_put(pppx_if_pl, pxi);
                error = ENOMEM;
-               rw_exit_write(&pppx_ifs_lk);
                goto out;
        }
 
@@ -846,14 +839,12 @@ pppx_add_session(struct pppx_dev *pxd, s
        if (RBT_FIND(pppx_ifs, &pppx_ifs, pxi) != NULL) {
                pool_put(pppx_if_pl, pxi);
                error = EADDRINUSE;
-               rw_exit_write(&pppx_ifs_lk);
                goto out;
        }
 
        if (RBT_INSERT(pppx_ifs, &pppx_ifs, pxi) != NULL)
                panic("%s: pppx_ifs modified while lock was held", __func__);
        LIST_INSERT_HEAD(&pxd->pxd_pxis, pxi, pxi_list);
-       rw_exit_write(&pppx_ifs_lk);
 
        snprintf(ifp->if_xname, sizeof(ifp->if_xname), "%s%d", "pppx", unit);
        ifp->if_mtu = req->pr_peer_mru; /* XXX */
@@ -935,9 +926,7 @@ pppx_add_session(struct pppx_dev *pxd, s
        } else {
                if_addrhooks_run(ifp);
        }
-       rw_enter_write(&pppx_ifs_lk);
        pxi->pxi_ready = 1;
-       rw_exit_write(&pppx_ifs_lk);
 
 out:
        return (error);
@@ -1038,11 +1027,9 @@ pppx_if_destroy(struct pppx_dev *pxd, st
        if_detach(ifp);
        NET_LOCK();
 
-       rw_enter_write(&pppx_ifs_lk);
        if (RBT_REMOVE(pppx_ifs, &pppx_ifs, pxi) == NULL)
                panic("%s: pppx_ifs modified while lock was held", __func__);
        LIST_REMOVE(pxi, pxi_list);
-       rw_exit_write(&pppx_ifs_lk);
 
        pool_put(pppx_if_pl, pxi);
 }