As mpi@ noticed malloc() with M_WAITOK can cause context switch too. I
wish to drop concurency while RBT pppx_ifs is accessed. So, remove
malloc() from pppx_if_find(). Looks like original code should do search
in the same way, but it didn't.
Index: sys/net/if_pppx.c
===================================================================
RCS file: /cvs/src/sys/net/if_pppx.c,v
retrieving revision 1.82
diff -u -p -r1.82 if_pppx.c
--- sys/net/if_pppx.c 7 Apr 2020 13:27:52 -0000 1.82
+++ sys/net/if_pppx.c 8 Apr 2020 13:18:07 -0000
@@ -643,20 +643,20 @@ pppx_if_next_unit(void)
struct pppx_if *
pppx_if_find(struct pppx_dev *pxd, int session_id, int protocol)
{
- struct pppx_if *s, *p;
- s = malloc(sizeof(*s), M_DEVBUF, M_WAITOK | M_ZERO);
-
- s->pxi_key.pxik_session_id = session_id;
- s->pxi_key.pxik_protocol = protocol;
+ struct pppx_if_key key;
+ struct pppx_if *pxi;
+ memset(&key, 0, sizeof(key));
+ key.pxik_session_id = session_id;
+ key.pxik_protocol = protocol;
+
rw_enter_read(&pppx_ifs_lk);
- p = RBT_FIND(pppx_ifs, &pppx_ifs, s);
- if (p && p->pxi_ready == 0)
- p = NULL;
+ 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);
- free(s, M_DEVBUF, sizeof(*s));
- return (p);
+ return pxi;
}
int
