diff options
| -rw-r--r-- | sys/kern/uipc_mbuf.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c index 4d832a8..1f6069e 100644 --- a/sys/kern/uipc_mbuf.c +++ b/sys/kern/uipc_mbuf.c @@ -234,9 +234,12 @@ mb_free_ext(struct mbuf *m) * This is tricky. We need to make sure to decrement the * refcount in a safe way but to also clean up if we're the * last reference. This method seems to do it without race. + * The volatile cast is required to emit the proper load + * instructions. Otherwise gcc will optimize the read outside + * of the while loop. */ while (dofree == 0) { - cnt = *(m->m_ext.ref_cnt); + cnt = *(volatile u_int *)(m->m_ext.ref_cnt); if (atomic_cmpset_int(m->m_ext.ref_cnt, cnt, cnt - 1)) { if (cnt == 1) dofree = 1; |
