Return-Path: MIME-Version: 1.0 In-Reply-To: <35c90d960909211829u71880f94j861055c61efc8c@mail.gmail.com> References: <113d36d80909110053ybd2c203xeda76bd36248bb17@mail.gmail.com> <1252657436.8931.52.camel@violet> <113d36d80909110828i1b53e8f5x5b913fb7861850fd@mail.gmail.com> <1252687514.8931.77.camel@violet> <113d36d80909140210n476f5826x1ae2ea621b57782c@mail.gmail.com> <35c90d960909211752u389e5d6dqbd4afe0e055c43d0@mail.gmail.com> <35c90d960909211829u71880f94j861055c61efc8c@mail.gmail.com> From: Nick Pelly Date: Tue, 22 Sep 2009 13:18:26 -0700 Message-ID: <35c90d960909221318m4b918d2dg3e2688a89427319a@mail.gmail.com> Subject: Re: kernel panic happens when disconnecting Bluetooth headset To: Lan Zhu Cc: Marcel Holtmann , linux-bluetooth@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 List-ID: On Mon, Sep 21, 2009 at 6:29 PM, Nick Pelly wrote: > On Mon, Sep 21, 2009 at 5:52 PM, Nick Pelly wrote: >> On Mon, Sep 14, 2009 at 2:10 AM, Lan Zhu wrote: >>> Hi Marcel, >>> >>> 2009/9/12 Marcel Holtmann : >>>> Hi Zhu, >>>> >>>>> >> We met a issue that kernel panic happens when disconnecting some k= inds >>>>> >> of Bluetooth headset, then we did some analysis and made some chan= ges >>>>> >> on kernel code which have avoided the panic happening. Would you >>>>> >> please help to check if our analysis and fix is correct? >>>>> >> >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> Issue description >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> On Android platform(kernel 2.6.29), disconnecting Bluetooth headse= t >>>>> >> may cause kernel panic on certain conditions. >>>>> >> >>>>> >> (Pre-condition is android paired with headset.) >>>>> >> Initiate the connection from android, disconnect it from android, = result is OK. >>>>> >> Initiate the connection from android, disconnect it from headset, = result is OK. >>>>> >> Initiate the connection from headset, disconnect it from headset, = result is OK. >>>>> >> Initiate the connection from headset, disconnect it from android, = for >>>>> >> Motorola H12 headset, result is OK. >>>>> >> Initiate the connection from headset, disconnect it from android, = for >>>>> >> Motorola H620/560 headset, result is kernel panic. >>>>> >> >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> Kernel panic point >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> kernel panic at __list_del() in the function rfcomm_session_del() = , >>>>> >> panic reason is "Unable to handle kernel paging request at virtual >>>>> >> address 00200200" >>>>> >> >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> Kernel log analysis >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> rfcomm_session_del() is still called after the session entry is >>>>> >> removed from the list. Then __list_del() will cause kernel panic >>>>> >> because of the incorrect pointer. This situation occurs when calli= ng >>>>> >> rfcomm_recv_ua() when the socket state is BT_CLOSED . So we need t= o >>>>> >> find out why the socket state become BT_CLOSED before we calling >>>>> >> rfcomm_recv_ua(). >>>>> >> >>>>> >> # [ =A0171.677429] rfcomm_sock_sendmsg: sock ce9a0960, sk cc5c4c00 >>>>> >> [ =A0171.683532] rfcomm_dlc_send: dlc cd3fe920 mtu 255 len 14 >>>>> >> [ =A0171.689422] rfcomm_process_rx: session cc751be0 state 1 qlen = 0 >>>>> >> [ =A0171.695709] rfcomm_process_rx: @@@ @@@ sk_state =3D 1 >>>>> >> [ =A0171.701110] rfcomm_process_dlcs: session cc751be0 state 1 >>>>> >> [ =A0171.706939] rfcomm_process_tx: dlc cd3fe920 state 1 cfc 40 >>>>> >> rx_credits 33 tx_credits 31 >>>>> >> [ =A0171.715515] rfcomm_send_frame: session cc751be0 len 18 >>>>> >> [ =A0171.721130] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 3 >>>>> >> [ =A0174.127807] rfcomm_sock_sendmsg: sock ce9a0960, sk cc5c4c00 >>>>> >> [ =A0174.134490] rfcomm_dlc_send: dlc cd3fe920 mtu 255 len 6 >>>>> >> [ =A0174.141540] rfcomm_process_rx: session cc751be0 state 1 qlen = 0 >>>>> >> [ =A0174.148498] rfcomm_process_rx: @@@ @@@ sk_state =3D 1 >>>>> >> [ =A0174.154968] rfcomm_process_dlcs: session cc751be0 state 1 >>>>> >> [ =A0174.161437] rfcomm_process_tx: dlc cd3fe920 state 1 cfc 40 >>>>> >> rx_credits 33 tx_credits 30 >>>>> >> [ =A0174.171173] rfcomm_send_frame: session cc751be0 len 10 >>>>> >> [ =A0174.177642] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 3 >>>>> >> [ =A0174.205932] rfcomm_sock_release: sock ce9a0960, sk cc5c4c00 >>>>> >> [ =A0174.212707] rfcomm_sock_shutdown: sock ce9a0960, sk cc5c4c00 >>>>> >> [ =A0174.220031] __rfcomm_sock_close: sk cc5c4c00 state 1 socket c= e9a0960 >>>>> >> [ =A0174.227508] __rfcomm_dlc_close: dlc cd3fe920 state 1 dlci 20 = err 0 >>>>> >> session cc751be0 >>>>> >> [ =A0174.236877] rfcomm_send_disc: cc751be0 dlci 20 >>>>> >> [ =A0174.242706] rfcomm_send_frame: session cc751be0 len 4 >>>>> >> [ =A0174.248962] rfcomm_dlc_set_timer: dlc cd3fe920 state 8 timeou= t 2560 >>>>> >> [ =A0174.256835] rfcomm_sock_kill: sk cc5c4c00 state 1 refcnt 2 >>>>> >> [ =A0174.263336] rfcomm_sock_destruct: sk cc5c4c00 dlc cd3fe920 >>>>> >> [ =A0174.399444] rfcomm_l2data_ready: ccf70400 bytes 4 >>>>> >> [ =A0174.404724] rfcomm_process_rx: session cc751be0 state 1 qlen = 1 >>>>> >> [ =A0174.411010] rfcomm_process_rx: @@@ @@@ sk_state =3D 1 >>>>> >> [ =A0174.416412] rfcomm_recv_ua: session cc751be0 state 1 dlci 20 >>>>> >> [ =A0174.422515] __rfcomm_dlc_close: dlc cd3fe920 state 9 dlci 20 = err 0 >>>>> >> session cc751be0 >>>>> >> [ =A0174.430816] rfcomm_dlc_clear_timer: dlc cd3fe920 state 9 >>>>> >> [ =A0174.436553] rfcomm_dlc_unlink: dlc cd3fe920 refcnt 1 session = cc751be0 >>>>> >> [ =A0174.443572] rfcomm_dlc_free: cd3fe920 >>>>> >> [ =A0174.447570] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 3 >>>>> >> [ =A0174.454528] rfcomm_send_disc: cc751be0 dlci 0 >>>>> >> [ =A0174.459259] rfcomm_send_frame: session cc751be0 len 4 >>>>> >> [ =A0174.464904] rfcomm_process_dlcs: session cc751be0 state 8 >>>>> >> [ =A0174.470703] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 2 >>>>> >> [ =A0174.898284] rfcomm_l2data_ready: ccf70400 bytes 4 >>>>> >> [ =A0174.903442] rfcomm_l2state_change: ccf70400 state 9 >>>>> >> [ =A0174.908874] rfcomm_process_rx: session cc751be0 state 8 qlen = 1 >>>>> >> [ =A0174.915130] rfcomm_process_rx: @@@ @@@ sk_state =3D 9 >>>>> >> [ =A0174.920562] rfcomm_recv_ua: session cc751be0 state 8 dlci 0 >>>>> >> [ =A0174.926574] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 2 >>>>> >> [ =A0174.933532] rfcomm_process_rx: @@@ @@@ sk_state =3D=3D BT_CLO= SED , s->initiator=3D0 >>>>> >> [ =A0174.941253] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 1 >>>>> >> [ =A0174.948211] rfcomm_session_del: session cc751be0 state 8 >>>>> >> [ =A0174.953918] @@@@ in rfcomm_session_del() >>>>> >> [ =A0174.958312] @@@@ s->list =3D cc751be0 >>>>> >> [ =A0174.962097] @@@@ s->list.next =3D ccbfe9a0 >>>>> >> [ =A0174.966369] @@@@ s->list.prev =3D c047d524 >>>>> >> [ =A0174.970733] @@@@ list is valid, call list_del() >>>>> >> [ =A0174.975646] @@@@ after list_del() >>>>> >> [ =A0174.979278] @@@@ s->list =3D cc751be0 >>>>> >> [ =A0174.983184] @@@@ s->list.next =3D 00100100 >>>>> >> [ =A0174.987457] @@@@ s->list.prev =3D 00200200 >>>>> >> [ =A0174.991729] rfcomm_session_close: session cc751be0 state 8 er= r 104 >>>>> >> [ =A0174.998504] rfcomm_session_put: in rfcomm_session_put, s->ref= cnt =3D 1 >>>>> >> [ =A0175.005310] rfcomm_session_del: session cc751be0 state 9 >>>>> >> [ =A0175.011169] @@@@ in rfcomm_session_del() >>>>> >> [ =A0175.015441] @@@@ s->list =3D cc751be0 >>>>> >> [ =A0175.019409] @@@@ s->list.next =3D 00100100 >>>>> >> [ =A0175.023651] @@@@ s->list.prev =3D 00200200 >>>>> >> [ =A0175.027923] @@@@ list is valid, call list_del() >>>>> >> [ =A0175.032958] Unable to handle kernel paging request at virtual >>>>> >> address 00200200 >>>>> >> [ =A0175.040679] pgd =3D c0004000 >>>>> >> [ =A0175.043792] [00200200] *pgd=3D00000000 >>>>> >> [ =A0175.047821] Internal error: Oops: 817 [#1] >>>>> >> [ =A0175.052246] Modules linked in: >>>>> >> [ =A0175.055725] CPU: 0 =A0 =A0Not tainted =A0(2.6.29-omap1-dirty = #34) >>>>> >> [ =A0175.061859] PC is at rfcomm_session_del+0x6c/0x108 >>>>> >> [ =A0175.067047] LR is at release_console_sem+0x190/0x1a0 >>>>> >> [ =A0175.072509] pc : [] =A0 =A0lr : [] =A0 = =A0psr: 60000013 >>>>> >> [ =A0175.072509] sp : cc1abf38 =A0ip : cc1abe68 =A0fp : cc1abf4c >>>>> >> [ =A0175.084960] r10: cc751c04 =A0r9 : c036d2fc =A0r8 : cc751be0 >>>>> >> [ =A0175.090545] r7 : 00000068 =A0r6 : cc751c04 =A0r5 : 00000009 = =A0r4 : cc751be0 >>>>> >> [ =A0175.097656] r3 : 00100100 =A0r2 : 00100100 =A0r1 : 00200200 = =A0r0 : c0422876 >>>>> >> >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> HCI log analysis >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> Compare the hcidump log of the correct case with the one of the pa= nic >>>>> >> case, we found there is only one difference in the message sequenc= e. >>>>> >> In the panic case, headset send L2CAP Disconn_Req immediately afte= r >>>>> >> sending rfcomm UA frame to android. We think this is the reason th= at >>>>> >> cause the socket state become BT_CLOSED. >>>>> >> >>>>> >> Please compare these two log, pay attention to the message directi= on >>>>> >> of the last Disconn_Req. >>>>> >> >>>>> >> >>>>> >> Log of correct case: >>>>> >> ---------------------------- >>>>> >> >>>>> >> >>>>> >> 009-09-10 15:27:28.963519 < ACL data: handle 1 flags 0x02 dlen 22 >>>>> >> =A0 =A0L2CAP(d): cid 0x0047 len 18 [psm 3] >>>>> >> =A0 =A0 =A0RFCOMM(d): UIH: cr 0 dlci 20 pf 0 ilen 14 fcs 0xeb >>>>> >> =A0 =A0 =A00000: 0d 0a 2b 43 49 45 56 3a =A020 37 2c 33 0d 0a =A0 = =A0 =A0 =A0..+CIEV: 7,3.. >>>>> >> 009-09-10 15:27:28.967272 > HCI Event: Number of Completed Packets= (0x13) plen >>>>> >> >>>>> >> =A0 =A0handle 1 packets 1 >>>>> >> 009-09-10 15:27:29.243945 < ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0L2CAP(d): cid 0x0047 len 4 [psm 3] >>>>> >> =A0 =A0 =A0RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d >>>>> >> 009-09-10 15:27:29.247363 > HCI Event: Number of Completed Packets= (0x13) plen >>>>> >> >>>>> >> =A0 =A0handle 1 packets 1 >>>>> >> 009-09-10 15:27:29.274890 > ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0L2CAP(d): cid 0x0040 len 4 [psm 3] >>>>> >> =A0 =A0 =A0RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57 >>>>> >> 009-09-10 15:27:29.296343 < ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0L2CAP(d): cid 0x0047 len 4 [psm 3] >>>>> >> =A0 =A0 =A0RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c >>>>> >> 009-09-10 15:27:29.298480 > HCI Event: Number of Completed Packets= (0x13) plen >>>>> >> >>>>> >> =A0 =A0handle 1 packets 1 >>>>> >> 009-09-10 15:27:29.319873 > ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0L2CAP(d): cid 0x0040 len 4 [psm 3] >>>>> >> =A0 =A0 =A0RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6 >>>>> >> 009-09-10 15:27:29.320727 < ACL data: handle 1 flags 0x02 dlen 12 >>>>> >> =A0 =A0L2CAP(s): Disconn req: dcid 0x0047 scid 0x0040 >>>>> >> 009-09-10 15:27:29.323474 > HCI Event: Number of Completed Packets= (0x13) plen >>>>> >> >>>>> >> =A0 =A0handle 1 packets 1 >>>>> >> 009-09-10 15:27:29.337237 > ACL data: handle 1 flags 0x02 dlen 12 >>>>> >> =A0 =A0L2CAP(s): Disconn rsp: dcid 0x0047 scid 0x0040 >>>>> >> >>>>> >> >>>>> >> >>>>> >> >>>>> >> log of panic case: >>>>> >> ------------------------ >>>>> >> >>>>> >> >>>>> >> >>>>> >> 2009-09-10 13:34:24.020208 < ACL data: handle 1 flags 0x02 dlen 22 >>>>> >> =A0 =A0 L2CAP(d): cid 0x0041 len 18 [psm 3] >>>>> >> =A0 =A0 =A0 RFCOMM(d): UIH: cr 0 dlci 20 pf 0 ilen 14 fcs 0xeb >>>>> >> =A0 =A0 =A0 0000: 0d 0a 2b 43 49 45 56 3a =A020 37 2c 33 0d 0a =A0= =A0 =A0 =A0..+CIEV: 7,3.. >>>>> >> 2009-09-10 13:34:24.281256 > HCI Event: Number of Completed Packet= s (0x13) plen >>>>> >> 5 >>>>> >> =A0 =A0 handle 1 packets 1 >>>>> >> 2009-09-10 13:34:24.083580 < ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0 L2CAP(d): cid 0x0041 len 4 [psm 3] >>>>> >> =A0 =A0 =A0 RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d >>>>> >> 2009-09-10 13:34:24.529442 > HCI Event: Number of Completed Packet= s (0x13) plen >>>>> >> 5 >>>>> >> =A0 =A0 handle 1 packets 1 >>>>> >> 2009-09-10 13:34:24.531914 > ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0 L2CAP(d): cid 0x0040 len 4 [psm 3] >>>>> >> =A0 =A0 =A0 RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57 >>>>> >> 2009-09-10 13:34:24.533135 < ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0 L2CAP(d): cid 0x0041 len 4 [psm 3] >>>>> >> =A0 =A0 =A0 RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c >>>>> >> 2009-09-10 13:34:25.028649 > HCI Event: Number of Completed Packet= s (0x13) plen >>>>> >> 5 >>>>> >> =A0 =A0 handle 1 packets 1 >>>>> >> 2009-09-10 13:34:25.032128 > ACL data: handle 1 flags 0x02 dlen 8 >>>>> >> =A0 =A0 L2CAP(d): cid 0x0040 len 4 [psm 3] >>>>> >> =A0 =A0 =A0 RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6 >>>>> >> 2009-09-10 13:34:25.032341 > ACL data: handle 1 flags 0x02 dlen 12 >>>>> >> =A0 =A0 L2CAP(s): Disconn req: dcid 0x0040 scid 0x0041 >>>>> >> 2009-09-10 13:34:25.032646 < ACL data: handle 1 flags 0x02 dlen 12 >>>>> >> =A0 =A0 L2CAP(s): Disconn rsp: dcid 0x0040 scid 0x0041 >>>>> >> >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> Analysis Result >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> For some kinds of Bluetooth headset such as Motorola H560/H620 whi= ch >>>>> >> are based on BCM2044S, they will send L2CAP Disconn_Req command ri= ght >>>>> >> after sending rfcomm UA frame. This L2CAP Disconn_Req will cause t= he >>>>> >> rfcomm socket state become BT_CLOSED before completely handling UA >>>>> >> frame, thus it will cause kernel panic. I think we can ignore the >>>>> >> received rfcomm frames if socket state is BT_CLOSED, because it >>>>> >> doesn't make sense in the BT_CLOSED state. >>>>> >> >>>>> >> >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> Changed Code >>>>> >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> >> We changed the code in the function rfcomm_process_rx() in >>>>> >> net/bluetooth/rfcomm/core.c, check the socket state first before >>>>> >> handling the received framew. If the socket state is BT_CLOSED, we >>>>> >> don't handle any rfcomm frames but just close the session. >>>>> >> >>>>> >> The change is like below >>>>> >> >>>>> >> + =A0 =A0 =A0 if (sk->sk_state !=3D BT_CLOSED) { >>>>> >> =A0 =A0 =A0 =A0 /* Get data directly from socket receive queue wit= hout copying it. */ >>>>> >> =A0 =A0 =A0 =A0 while ((skb =3D skb_dequeue(&sk->sk_receive_queue)= )) { >>>>> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 skb_orphan(skb); >>>>> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 rfcomm_recv_frame(s, skb); >>>>> >> =A0 =A0 =A0 =A0 } >>>>> >> - >>>>> >> - =A0 =A0 =A0 if (sk->sk_state =3D=3D BT_CLOSED) { >>>>> >> + =A0 =A0 =A0 } else { >>>>> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (!s->initiator) >>>>> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 rfcomm_session_put= (s); >>>>> >> >>>>> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 rfcomm_session_close(s, sk->sk_err= ); >>>>> >> =A0 =A0 =A0 =A0 =A0} >>>>> > >>>>> > so I do see the issue here, but I don't agree with the fix since it >>>>> > changes behavior that might cause other issues. So in case the fram= e >>>>> > processing leads to sk->sk_state =3D=3D BT_CLOSED we are not closin= g the >>>>> > connection anymore if we make it depend on a state before the frame >>>>> > processing. And nothing guarantees that rfcomm_process_rx gets sche= duled >>>>> > again. >>>>> > >>>>> > diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/cor= e.c >>>>> > index 94b3388..606143b 100644 >>>>> > --- a/net/bluetooth/rfcomm/core.c >>>>> > +++ b/net/bluetooth/rfcomm/core.c >>>>> > @@ -1798,12 +1798,16 @@ static inline void rfcomm_process_rx(struct= rfcomm_session *s) >>>>> > >>>>> > =A0 =A0 =A0 =A0BT_DBG("session %p state %ld qlen %d", s, s->state, = skb_queue_len(&sk->sk_receive_queue)); >>>>> > >>>>> > + =A0 =A0 =A0 rfcomm_session_hold(s); >>>>> > + >>>>> > =A0 =A0 =A0 =A0/* Get data directly from socket receive queue witho= ut copying it. */ >>>>> > =A0 =A0 =A0 =A0while ((skb =3D skb_dequeue(&sk->sk_receive_queue)))= { >>>>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0skb_orphan(skb); >>>>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0rfcomm_recv_frame(s, skb); >>>>> > =A0 =A0 =A0 =A0} >>>>> > >>>>> > + =A0 =A0 =A0 rfcomm_session_put(s); >>>>> > + >>>>> > =A0 =A0 =A0 =A0if (sk->sk_state =3D=3D BT_CLOSED) { >>>>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (!s->initiator) >>>>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0rfcomm_session_put(s= ); >>>>> > >>>>> > What does the above patch do for you? Since if I read it correctly,= then >>>>> > the rfcomm_recv_ua causes the rfcomm_session_put to trigger the clo= sing >>>>> > of the session. And then in this case it is delayed until after all >>>>> > frames are processed. >>>>> > >>>>> > >>>>> >>>>> I've tried your patch but unfortunately kernel panic still happened. >>>>> >>>>> From the log I noticed that if rfcomm_l2state_change is called before >>>>> rfcomm_process_rx, kernel panic will happen definitely. >>>>> >>>>> Below lines are in the correct log, >>>>> >>>>> [ =A0139.323852] rfcomm_l2data_ready: ccf70000 bytes 4 >>>>> [ =A0139.346252] rfcomm_process_rx: session ccb94ce0 state 8 qlen 1 >>>>> ... >>>>> [ =A0139.457519] rfcomm_l2state_change: ccf70000 state 9 >>>>> (disconnect ok) >>>>> >>>>> In the above case, when process_rx, the code in the condition "if >>>>> (sk->sk_state =3D=3D BT_CLOSED)" will never run. >>>>> >>>>> Below lines are in the panic log, >>>>> >>>>> [ =A0174.898284] rfcomm_l2data_ready: ccf70400 bytes 4 >>>>> [ =A0174.903442] rfcomm_l2state_change: ccf70400 state 9 >>>>> [ =A0174.908874] rfcomm_process_rx: session cc751be0 state 8 qlen 1 >>>>> ... >>>>> ( then panic) >>>>> >>>>> In the above case, sk_state is changed to 9 (BT_CLOSED) firstly, =A0t= hen >>>>> process_rx, so the code in the condition "if (sk->sk_state =3D=3D >>>>> BT_CLOSED) " will be run, it will call session_put twice. I think thi= s >>>>> is the root cause of panic. >>>> >>>> I know why it happens, that is not the problem. My point is not to bre= ak >>>> current scheduling assumptions. >>>> >>>> So if you move the rfcomm_session_put() now at the end of the function= , >>>> then it should be fine, right? >>>> >>>> Regards >>>> >>>> Marcel >>>> >>>> >>>> >>> >>> You are right. I moved the rfcomm_session_put() at the end of >>> rfcomm_process_tx() then kernel panic doesn't happen any longer. >>> >>> The changed code is like below, >>> >>> @@ -1796,6 +1796,8 @@ static inline void rfcomm_process_rx(struct rfcom= m_session >>> >>> =A0 =A0 =A0 =A0BT_DBG("session %p state %ld qlen %d", s, s->state, skb_= queue_len(&sk->s >>> >>> + =A0 =A0 =A0 rfcomm_session_hold(s); >>> + >>> =A0 =A0 =A0 =A0/* Get data directly from socket receive queue without c= opying it. */ >>> =A0 =A0 =A0 =A0while ((skb =3D skb_dequeue(&sk->sk_receive_queue))) { >>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0skb_orphan(skb); >>> @@ -1808,6 +1810,8 @@ static inline void rfcomm_process_rx(struct rfcom= m_session >>> >>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0rfcomm_session_close(s, sk->sk_err); >>> =A0 =A0 =A0 =A0} >>> + >>> + =A0 =A0 =A0 rfcomm_session_put(s); >>> =A0} >>> >>> =A0static inline void rfcomm_accept_connection(struct rfcomm_session *s= ) >>> >>> Please submit this change to bluez release. >> >> >> Unfortunately, with this change I get a panic disconnecting from >> Motorola H270 in the case that the headset initiated RFCOMM and we >> disconnect RFCOMM. >> >> Here is the hcidump: >> >> 2009-09-21 17:22:37.384811 < ACL data: handle 1 flags 0x02 dlen 22 >> =A0 =A0L2CAP(d): cid 0x0041 len 18 [psm 3] >> =A0 =A0 =A0RFCOMM(d): UIH: cr 0 dlci 20 pf 0 ilen 14 fcs 0xeb >> =A0 =A0 =A00000: 0d 0a 2b 43 49 45 56 3a =A020 37 2c 33 0d 0a =A0 =A0 = =A0 =A0..+CIEV: 7,3.. >> 2009-09-21 17:22:37.502273 > HCI Event: Number of Completed Packets >> (0x13) plen 5 >> =A0 =A0handle 1 packets 1 >> 2009-09-21 17:22:37.788895 < ACL data: handle 1 flags 0x02 dlen 8 >> =A0 =A0L2CAP(d): cid 0x0041 len 4 [psm 3] >> =A0 =A0 =A0RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d >> 2009-09-21 17:22:37.906204 > HCI Event: Number of Completed Packets >> (0x13) plen 5 >> =A0 =A0handle 1 packets 1 >> 2009-09-21 17:22:37.933090 > ACL data: handle 1 flags 0x02 dlen 8 >> =A0 =A0L2CAP(d): cid 0x0040 len 4 [psm 3] >> =A0 =A0 =A0RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57 >> 2009-09-21 17:22:38.636764 < ACL data: handle 1 flags 0x02 dlen 8 >> =A0 =A0L2CAP(d): cid 0x0041 len 4 [psm 3] >> =A0 =A0 =A0RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c >> 2009-09-21 17:22:38.744125 > HCI Event: Number of Completed Packets >> (0x13) plen 5 >> =A0 =A0handle 1 packets 1 >> 2009-09-21 17:22:38.763687 > ACL data: handle 1 flags 0x02 dlen 8 >> =A0 =A0L2CAP(d): cid 0x0040 len 4 [psm 3] >> =A0 =A0 =A0RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6 >> 2009-09-21 17:22:38.783554 > ACL data: handle 1 flags 0x02 dlen 12 >> =A0 =A0L2CAP(s): Disconn req: dcid 0x0040 scid 0x0041 >> 2009-09-21 17:22:39.029526 < ACL data: handle 1 flags 0x02 dlen 12 >> =A0 =A0L2CAP(s): Disconn rsp: dcid 0x0040 scid 0x0041 >> 2009-09-21 17:22:39.136581 > HCI Event: Number of Completed Packets >> (0x13) plen 5 >> =A0 =A0handle 1 packets 1 >> 2009-09-21 17:22:41.337203 > HCI Event: Disconn Complete (0x05) plen 4 >> =A0 =A0status 0x00 handle 1 reason 0x13 >> =A0 =A0Reason: Remote User Terminated Connection >> >> And the panic: >> >> <7>[ 3161.665557] rfcomm:rfcomm_session_del: session c9c06ad0 state 9 >> <7>[ 3161.671905] l2cap:l2cap_sock_release: sock cea04360, sk c97f02f8 >> <7>[ 3161.678497] l2cap:l2cap_sock_shutdown: sock cea04360, sk c97f02f8 >> <7>[ 3161.685028] l2cap:l2cap_sock_kill: sk c97f02f8 state 9 >> <7>[ 3161.695587] l2cap:l2cap_sock_destruct: sk c97f02f8 >> <4>[ 3161.700805] npelly 1911 rfcomm_process_sessions session c9c06ad0 >> refcnt 1802201963 >> <7>[ 3161.709014] rfcomm:rfcomm_process_dlcs: session c9c06ad0 state 180= 2201963 >> <7>[ 3161.716308] rfcomm:rfcomm_process_dlcs: session c9c06ad0 dlc 6b6b6= b6b >> <1>[ 3161.726776] Unable to handle kernel paging request at virtual >> address 6b6b6b6b >> <1>[ 3161.734619] pgd =3D c0004000 >> <1>[ 3161.737609] [6b6b6b6b] *pgd=3D00000000 >> <4>[ 3161.741638] Internal error: Oops: 5 [#1] PREEMPT >> <4>[ 3161.746734] Modules linked in: >> <4>[ 3161.750213] CPU: 0 =A0 =A0Not tainted >> (2.6.29-omap1-07358-g9a3fd55-dirty #206) >> <4>[ 3161.757629] PC is at rfcomm_process_dlcs+0x108/0x590 >> <4>[ 3161.762969] LR is at preempt_schedule+0x44/0x54 >> <4>[ 3161.767852] pc : [] =A0 =A0lr : [] =A0 =A0psr:= 60000113 >> <4>[ 3161.767883] sp : ccdf9e80 =A0ip : ccdf9dd8 =A0fp : ccdf9edc >> <4>[ 3161.780273] r10: 00000000 =A0r9 : c9c06af4 =A0r8 : c9c06ad0 >> <4>[ 3161.786010] r7 : 00000000 =A0r6 : c9c06ad0 =A0r5 : c4c68680 =A0r4 = : 6b6b6b6b >> <4>[ 3161.792968] r3 : c9c06ae0 =A0r2 : ccdf8000 =A0r1 : c61a8940 =A0r0 = : 0000004c >> <4>[ 3161.800079] Flags: nZCv =A0IRQs on =A0FIQs on =A0Mode SVC_32 =A0IS= A ARM >> Segment kernel >> <4>[ 3161.807983] Control: 10c5387d =A0Table: 86db8019 =A0DAC: 00000017 >> <4>[ 3161.814147] >> <4>[ 3161.814147] PC: 0xc0391174: >> [...] >> <4>[ 3162.973175] Backtrace: >> <4>[ 3162.976013] [] (rfcomm_process_dlcs+0x0/0x590) from >> [] (rfcomm_process_sessions+0x1a34/0x1a9c) >> <4>[ 3162.987579] [] (rfcomm_process_sessions+0x0/0x1a9c) >> from [] (rfcomm_run+0x1d4/0x2ac) >> <4>[ 3162.998199] [] (rfcomm_run+0x0/0x2ac) from >> [] (kthread+0x5c/0x94) >> <4>[ 3163.013763] [] (kthread+0x0/0x94) from [] >> (do_exit+0x0/0x714) >> >> >> Seems like this fix avoids the panic due to calling >> rfcomm_session_close() on a deleted session, but does not always >> address the unbalanced rfcomm_session_put() which may be the root >> cause. >> >> Lan Zhu suspected this in the original post, and his original fix does >> in fact fix this panic as well as the originally reported panic, >> because it avoids the unbalanced rfcomm_session_put(). >> >> Marcel I know you are concerned about the original fix changing >> scheduling assumptions, are you able to comment on this further? >> >> Are there any other suggestions for patches for this issue? I have >> spent the best part of the day trying to figure this one out, but the >> recounting in the rfcomm core is quite subtle and I think it really >> needs someone familiar with the code to have a quick look and come up >> with the safest patch. I can run tests. >> >> In the mean time, I am doing some testing of Lan Zhu's original fix >> and if there are no better suggestions we will run with that one for >> Android. >> >> Nick >> >> >> Some more analysis: >> >> With the RFCOMM connection in idle there are 2 references on s->refcnt >> >> However three references are removed during disconnect with the H270 >> - rfcomm_process_sessions() -> __rfcomm_dlc_close() -> rfcomm_dlc_unlink= () >> - rfcomm_process_sessions() -> rfcomm_process_rx() -> rfcomm_recv_ua() >> with dlci =3D 0 and s->state =3D BT_DISCONN >> - rfcomm_process_sessions() -> rfcomm_process_rx() with sk_state =3D >> BT_CLOSED and s->initiator =3D 0 >> >> in that order. >> >> On another headset, for example the Moto H350, we only see the first >> two references removed during disconnect. >> >> - rfcomm_process_sessions() -> __rfcomm_dlc_close() -> rfcomm_dlc_unlink= () >> - rfcomm_process_sessions() -> rfcomm_process_rx() -> rfcomm_recv_ua() >> with dlci =3D 0 and s->state =3D BT_DISCONN >> > > How about this. We still call rfcomm_process_rx(), but avoid the > rfcomm_session_put() due to RFCOMM UA when the socket state is > BT_CLOSED. > > It is less invasive, so might address Marcel's concerns with regard to > scheduling changes. > > > diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c > index c109a3a..333c6e9 100644 > --- a/net/bluetooth/rfcomm/core.c > +++ b/net/bluetooth/rfcomm/core.c > @@ -1105,6 +1105,8 @@ static int rfcomm_recv_ua(struct rfcomm_session > *s, u8 dlci) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} > =A0 =A0 =A0 =A0} else { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0/* Control channel */ > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 struct socket *sock =3D s->sock; > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 struct sock *sk =3D sock->sk; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0switch (s->state) { > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0case BT_CONNECT: > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0s->state =3D BT_CONNECTED; > @@ -1112,7 +1114,8 @@ static int rfcomm_recv_ua(struct rfcomm_session > *s, u8 dlci) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0break; > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0case BT_DISCONN: > - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 rfcomm_session_put(s); > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (sk->sk_state !=3D BT_CL= OSED) > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 rfcomm_sess= ion_put(s); > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0break; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} > =A0 =A0 =A0 =A0} > I made a minor style improvement and added commit message. Patch available = from http://android.git.kernel.org/?p=3Dkernel/common.git;a=3Dcommit;h=3D1048e00= 7842da2d6440679e1ca80f45438a6369d Nick