Re: [PATCH] Bluetooth: hidp: might sleep error in hidp_session_thread

[jeffy]

Hi brian,

On 01/24/2017 10:31 AM, Brian Norris wrote:

Hi Jeffy,

On Fri, Jan 20, 2017 at 09:52:08PM +0800, Jeffy Chen wrote:

[   39.044329] do not call blocking ops when !TASK_RUNNING; state=1 set
at [] hidp_session_thread+0x110/0x568 [hidp]
...
[   40.159664] Call trace:
[   40.162122] [] __might_sleep+0x64/0x90
[   40.167443] [] lock_sock_nested+0x30/0x78
[   40.173047] [] l2cap_sock_sendmsg+0x90/0xf0
[bluetooth]
[   40.179842] [] sock_sendmsg+0x4c/0x68
[   40.185072] [] kernel_sendmsg+0x54/0x68
[   40.190477] [] hidp_send_frame+0x78/0xa0 [hidp]
[   40.196574] [] hidp_process_transmit+0x44/0x98
[hidp]
[   40.203191] [] hidp_session_thread+0x364/0x568
[hidp]

Am I crazy, or are several other protocols broken like this too? I see a
similar structure in net/bluetooth/bnep/core.c and
net/bluetooth/cmtp/core.c, at least, each of which also call
kernel_sendmsg(), which might be an l2cap socket (...I think? I'm not a
bluetooth expert really).
Thanx, uploaded a new serial of patchset, which contains hidp & cmtp & 
bnep:9534023/9534025/9534027



Following (https://lwn.net/Articles/628628/).

Signed-off-by: Jeffy Chen 
---

  net/bluetooth/hidp/core.c | 15 +--
  1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 0bec458..bfd3fb8 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -1180,7 +1180,9 @@ static void hidp_session_run(struct hidp_session *session)
struct sock *ctrl_sk = session->ctrl_sock->sk;
struct sock *intr_sk = session->intr_sock->sk;
struct sk_buff *skb;
+   DEFINE_WAIT_FUNC(wait, woken_wake_function);
  
+	add_wait_queue(sk_sleep(intr_sk), );

for (;;) {
/*
 * This thread can be woken up two ways:
@@ -1188,12 +1190,10 @@ static void hidp_session_run(struct hidp_session 
*session)
 *session->terminate flag and wakes this thread up.
 *  - Via modifying the socket state of ctrl/intr_sock. This
 *thread is woken up by ->sk_state_changed().
-*
-* Note: set_current_state() performs any necessary
-* memory-barriers for us.
 */
-   set_current_state(TASK_INTERRUPTIBLE);
  
+		/* Ensure session->terminate is updated */

+   smp_mb__before_atomic();
if (atomic_read(>terminate))
break;
  
@@ -1227,11 +1227,14 @@ static void hidp_session_run(struct hidp_session *session)

hidp_process_transmit(session, >ctrl_transmit,
  session->ctrl_sock);
  
-		schedule();

+   wait_woken(, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);

I think this looks mostly good, except what about the
hidp_session_terminate() condition? In that case, you're running
wake_up_process() -- which won't set WQ_FLAG_WOKEN for us. So what
happens if we see a hidp_session_terminate() call in between the check
for the ->terminate count, but before we call wait_woken()? IIUC, I
think we'll just ignore the call and keep waiting for the next wake
signal.

I think you might need to rework hidp_session_terminate() too, to
actually target the wait queue and not just the processes.

IIUC, of course. I could be wrong...

Ok, that make sense, thanx for point that out.


Brian


}
+   remove_wait_queue(sk_sleep(intr_sk), );
  
  	atomic_inc(>terminate);

-   set_current_state(TASK_RUNNING);
+
+   /* Ensure session->terminate is updated */
+   smp_mb__after_atomic();
  }
  
  /*

--
2.1.4

Re: [PATCH] Bluetooth: hidp: might sleep error in hidp_session_thread

[Brian Norris]

Hi Jeffy,

On Fri, Jan 20, 2017 at 09:52:08PM +0800, Jeffy Chen wrote:
> [   39.044329] do not call blocking ops when !TASK_RUNNING; state=1 set
> at [] hidp_session_thread+0x110/0x568 [hidp]
> ...
> [   40.159664] Call trace:
> [   40.162122] [] __might_sleep+0x64/0x90
> [   40.167443] [] lock_sock_nested+0x30/0x78
> [   40.173047] [] l2cap_sock_sendmsg+0x90/0xf0
> [bluetooth]
> [   40.179842] [] sock_sendmsg+0x4c/0x68
> [   40.185072] [] kernel_sendmsg+0x54/0x68
> [   40.190477] [] hidp_send_frame+0x78/0xa0 [hidp]
> [   40.196574] [] hidp_process_transmit+0x44/0x98
> [hidp]
> [   40.203191] [] hidp_session_thread+0x364/0x568
> [hidp]

Am I crazy, or are several other protocols broken like this too? I see a
similar structure in net/bluetooth/bnep/core.c and
net/bluetooth/cmtp/core.c, at least, each of which also call
kernel_sendmsg(), which might be an l2cap socket (...I think? I'm not a
bluetooth expert really).

> 
> Following (https://lwn.net/Articles/628628/).
> 
> Signed-off-by: Jeffy Chen 
> ---
> 
>  net/bluetooth/hidp/core.c | 15 +--
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
> index 0bec458..bfd3fb8 100644
> --- a/net/bluetooth/hidp/core.c
> +++ b/net/bluetooth/hidp/core.c
> @@ -1180,7 +1180,9 @@ static void hidp_session_run(struct hidp_session 
> *session)
>   struct sock *ctrl_sk = session->ctrl_sock->sk;
>   struct sock *intr_sk = session->intr_sock->sk;
>   struct sk_buff *skb;
> + DEFINE_WAIT_FUNC(wait, woken_wake_function);
>  
> + add_wait_queue(sk_sleep(intr_sk), );
>   for (;;) {
>   /*
>* This thread can be woken up two ways:
> @@ -1188,12 +1190,10 @@ static void hidp_session_run(struct hidp_session 
> *session)
>*session->terminate flag and wakes this thread up.
>*  - Via modifying the socket state of ctrl/intr_sock. This
>*thread is woken up by ->sk_state_changed().
> -  *
> -  * Note: set_current_state() performs any necessary
> -  * memory-barriers for us.
>*/
> - set_current_state(TASK_INTERRUPTIBLE);
>  
> + /* Ensure session->terminate is updated */
> + smp_mb__before_atomic();
>   if (atomic_read(>terminate))
>   break;
>  
> @@ -1227,11 +1227,14 @@ static void hidp_session_run(struct hidp_session 
> *session)
>   hidp_process_transmit(session, >ctrl_transmit,
> session->ctrl_sock);
>  
> - schedule();
> + wait_woken(, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);

I think this looks mostly good, except what about the
hidp_session_terminate() condition? In that case, you're running
wake_up_process() -- which won't set WQ_FLAG_WOKEN for us. So what
happens if we see a hidp_session_terminate() call in between the check
for the ->terminate count, but before we call wait_woken()? IIUC, I
think we'll just ignore the call and keep waiting for the next wake
signal.

I think you might need to rework hidp_session_terminate() too, to
actually target the wait queue and not just the processes.

IIUC, of course. I could be wrong...

Brian

>   }
> + remove_wait_queue(sk_sleep(intr_sk), );
>  
>   atomic_inc(>terminate);
> - set_current_state(TASK_RUNNING);
> +
> + /* Ensure session->terminate is updated */
> + smp_mb__after_atomic();
>  }
>  
>  /*
> -- 
> 2.1.4
> 
> 

[PATCH] Bluetooth: hidp: might sleep error in hidp_session_thread

[Jeffy Chen]

[   39.044329] do not call blocking ops when !TASK_RUNNING; state=1 set
at [] hidp_session_thread+0x110/0x568 [hidp]
...
[   40.159664] Call trace:
[   40.162122] [] __might_sleep+0x64/0x90
[   40.167443] [] lock_sock_nested+0x30/0x78
[   40.173047] [] l2cap_sock_sendmsg+0x90/0xf0
[bluetooth]
[   40.179842] [] sock_sendmsg+0x4c/0x68
[   40.185072] [] kernel_sendmsg+0x54/0x68
[   40.190477] [] hidp_send_frame+0x78/0xa0 [hidp]
[   40.196574] [] hidp_process_transmit+0x44/0x98
[hidp]
[   40.203191] [] hidp_session_thread+0x364/0x568
[hidp]

Following (https://lwn.net/Articles/628628/).

Signed-off-by: Jeffy Chen 
---

 net/bluetooth/hidp/core.c | 15 +--
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 0bec458..bfd3fb8 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -1180,7 +1180,9 @@ static void hidp_session_run(struct hidp_session *session)
struct sock *ctrl_sk = session->ctrl_sock->sk;
struct sock *intr_sk = session->intr_sock->sk;
struct sk_buff *skb;
+   DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+   add_wait_queue(sk_sleep(intr_sk), );
for (;;) {
/*
 * This thread can be woken up two ways:
@@ -1188,12 +1190,10 @@ static void hidp_session_run(struct hidp_session 
*session)
 *session->terminate flag and wakes this thread up.
 *  - Via modifying the socket state of ctrl/intr_sock. This
 *thread is woken up by ->sk_state_changed().
-*
-* Note: set_current_state() performs any necessary
-* memory-barriers for us.
 */
-   set_current_state(TASK_INTERRUPTIBLE);
 
+   /* Ensure session->terminate is updated */
+   smp_mb__before_atomic();
if (atomic_read(>terminate))
break;
 
@@ -1227,11 +1227,14 @@ static void hidp_session_run(struct hidp_session 
*session)
hidp_process_transmit(session, >ctrl_transmit,
  session->ctrl_sock);
 
-   schedule();
+   wait_woken(, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
+   remove_wait_queue(sk_sleep(intr_sk), );
 
atomic_inc(>terminate);
-   set_current_state(TASK_RUNNING);
+
+   /* Ensure session->terminate is updated */
+   smp_mb__after_atomic();
 }
 
 /*
-- 
2.1.4