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Date:      Tue, 29 Sep 2020 20:46:25 +0000 (UTC)
From:      "Bjoern A. Zeeb" <bz@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r366268 - head/sys/dev/rtwn/usb
Message-ID:  <202009292046.08TKkPMm090233@repo.freebsd.org>
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Author: bz
Date: Tue Sep 29 20:46:25 2020
New Revision: 366268
URL: https://svnweb.freebsd.org/changeset/base/366268

Log:
  rtwn: narrow the epoch area
  
  Rather than placing the epoch around the entire receive loop which
  might call into rtwn_rx_frame() and USB and sleep, split the loop
  into two[1] and leave us with one unlock/lock cycle as well.
  
  PR:		249925
  Reported by:	thj, (rkoberman gmail.com)
  Tested by:	thj
  Suggested by:	adrian [1]
  Reviewed by:	adrian
  MFC after:	3 days
  Sponsored by:	The FreeBSD Foundation (initially, paniced my iwl lab host)
  Differential Revision:	https://reviews.freebsd.org/D26554

Modified:
  head/sys/dev/rtwn/usb/rtwn_usb_rx.c

Modified: head/sys/dev/rtwn/usb/rtwn_usb_rx.c
==============================================================================
--- head/sys/dev/rtwn/usb/rtwn_usb_rx.c	Tue Sep 29 20:29:07 2020	(r366267)
+++ head/sys/dev/rtwn/usb/rtwn_usb_rx.c	Tue Sep 29 20:46:25 2020	(r366268)
@@ -368,7 +368,7 @@ rtwn_bulk_rx_callback(struct usb_xfer *xfer, usb_error
 	struct rtwn_softc *sc = &uc->uc_sc;
 	struct ieee80211com *ic = &sc->sc_ic;
 	struct ieee80211_node *ni;
-	struct mbuf *m = NULL, *next;
+	struct mbuf *m0, *m = NULL, *next;
 	struct rtwn_data *data;
 
 	RTWN_ASSERT_LOCKED(sc);
@@ -400,24 +400,30 @@ tr_setup:
 		 * ieee80211_input() because here is at the end of a USB
 		 * callback and safe to unlock.
 		 */
+		m0 = m;
+		while (m != NULL) {
+			M_ASSERTPKTHDR(m);
+			m->m_pkthdr.PH_loc.ptr = rtwn_rx_frame(sc, m);
+			m = m->m_nextpkt;
+		}
 		NET_EPOCH_ENTER(et);
+		RTWN_UNLOCK(sc);
+		m = m0;
 		while (m != NULL) {
 			next = m->m_nextpkt;
 			m->m_nextpkt = NULL;
 
-			ni = rtwn_rx_frame(sc, m);
-
-			RTWN_UNLOCK(sc);
-
+			ni = m->m_pkthdr.PH_loc.ptr;
+			m->m_pkthdr.PH_loc.ptr = NULL;
 			if (ni != NULL) {
 				(void)ieee80211_input_mimo(ni, m);
 				ieee80211_free_node(ni);
 			} else {
 				(void)ieee80211_input_mimo_all(ic, m);
 			}
-			RTWN_LOCK(sc);
 			m = next;
 		}
+		RTWN_LOCK(sc);
 		NET_EPOCH_EXIT(et);
 		break;
 	default:

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