* Rename M_WAIT mbuf subsystem flag to M_TRYWAIT.

  This is because calls with M_WAIT (now M_TRYWAIT) may not wait
  forever when nothing is available for allocation, and may end up
  returning NULL. Hopefully we now communicate more of the right thing
  to developers and make it very clear that it's necessary to check whether
  calls with M_(TRY)WAIT also resulted in a failed allocation.
  M_TRYWAIT basically means "try harder, block if necessary, but don't
  necessarily wait forever." The time spent blocking is tunable with
  the kern.ipc.mbuf_wait sysctl.
  M_WAIT is now deprecated but still defined for the next little while.

* Fix a typo in a comment in mbuf.h

* Fix some code that was actually passing the mbuf subsystem's M_WAIT to
  malloc(). Made it pass M_WAITOK instead. If we were ever to redefine the
  value of the M_WAIT flag, this could have became a big problem.

1 files changed, 3 insertions, 3 deletions

diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index d5b8ec5e2e20..812764fefe38 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -548,7 +548,7 @@ sendit(p, s, mp, flags)
 		if (mp->msg_flags == MSG_COMPAT) {
 			register struct cmsghdr *cm;
 
-			M_PREPEND(control, sizeof(*cm), M_WAIT);
+			M_PREPEND(control, sizeof(*cm), M_TRYWAIT);
 			if (control == 0) {
 				error = ENOBUFS;
 				goto bad;
@@ -1331,7 +1331,7 @@ sockargs(mp, buf, buflen, type)
 #endif
 		return (EINVAL);
 	}
-	m = m_get(M_WAIT, type);
+	m = m_get(M_TRYWAIT, type);
 	if (m == NULL)
 		return (ENOBUFS);
 	m->m_len = buflen;
@@ -1702,7 +1702,7 @@ retry_lookup:
 		/*
 		 * Get an mbuf header and set it up as having external storage.
 		 */
-		MGETHDR(m, M_WAIT, MT_DATA);
+		MGETHDR(m, M_TRYWAIT, MT_DATA);
 		if (m == NULL) {
 			error = ENOBUFS;
 			sf_buf_free((void *)sf->kva, NULL);