From: Johan Hedberg <johan.hedberg@xxxxxxxxx>
Recent kernels have started giving the following style warnings:
[ +0.000237] WARNING: CPU: 1 PID: 701 at kernel/sched/core.c:7300 __might_sleep+0x65/0xa3()
[ +0.000407] do not call blocking ops when !TASK_RUNNING; state=1 set at [<f88b0955>] l2cap_sock_accept+0x97/0x1b4 [bluetooth]
[ +0.000611] Modules linked in: btusb hci_vhci rfcomm bluetooth
[ +0.000305] CPU: 1 PID: 701 Comm: l2cap-tester Not tainted 3.19.0-rc4+ #1304
[ +0.000318] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140709_153950- 04/01/2014
[ +0.000463] 00000000 00000000 f2e81c70 c13e57df f2e81c9c f2e81c8c c103372c 00001c84
[ +0.000586] c104e4a1 00000001 f5e93390 f5e93390 f2e81ca4 c103376e 00000009 f2e81c9c
[ +0.000422] c15da812 f2e81cb8 f2e81cdc c104e4a1 c15da2ae 00001c84 c15da812 00000001
[ +0.000869] Call Trace:
[ +0.000073] [<c13e57df>] dump_stack+0x49/0x73
[ +0.000182] [<c103372c>] warn_slowpath_common+0x89/0xa0
[ +0.000225] [<c104e4a1>] ? __might_sleep+0x65/0xa3
[ +0.000204] [<c103376e>] warn_slowpath_fmt+0x2b/0x2f
[ +0.000215] [<c104e4a1>] __might_sleep+0x65/0xa3
[ +0.000212] [<f88b0955>] ? l2cap_sock_accept+0x97/0x1b4 [bluetooth]
[ +0.000297] [<f88b0955>] ? l2cap_sock_accept+0x97/0x1b4 [bluetooth]
[ +0.000284] [<c130bfad>] lock_sock_nested+0x23/0x77
[ +0.000219] [<f888b25d>] bt_accept_dequeue+0x68/0x11b [bluetooth]
[ +0.000274] [<c1060165>] ? trace_hardirqs_on+0xb/0xd
[ +0.000224] [<f88b0985>] l2cap_sock_accept+0xc7/0x1b4 [bluetooth]
[ +0.000498] [<f88b0985>] ? l2cap_sock_accept+0xc7/0x1b4 [bluetooth]
[ +0.000494] [<c1051849>] ? wake_up_state+0x11/0x11
[ +0.000202] [<c1309c27>] SYSC_accept4+0xf3/0x1af
[ +0.000194] [<c11912b5>] ? security_socket_accept+0x14/0x16
[ +0.000252] [<c1309c27>] ? SYSC_accept4+0xf3/0x1af
[ +0.000201] [<c1061507>] ? lock_release_non_nested+0x137/0x217
[ +0.000256] [<c10cd5bc>] ? might_fault+0x44/0x8b
[ +0.000190] [<c10cd5bc>] ? might_fault+0x44/0x8b
[ +0.000196] [<c11da2b0>] ? _copy_from_user+0x44/0x4e
[ +0.000210] [<c130b3ea>] SYSC_socketcall+0xff/0x38c
[ +0.000205] [<c105fdcb>] ? mark_lock+0x1e/0x1c5
[ +0.000186] [<c10606d8>] ? __lock_acquire+0x342/0xc89
[ +0.000215] [<c1060926>] ? __lock_acquire+0x590/0xc89
[ +0.000217] [<c105ea2e>] ? __lock_is_held+0x2e/0x44
[ +0.000205] [<c11106c9>] ? fsnotify+0x452/0x494
[ +0.000186] [<c1060165>] ? trace_hardirqs_on+0xb/0xd
[ +0.000403] [<c10e4516>] ? fsnotify_modify+0x4a/0x55
[ +0.000497] [<c10e4516>] ? fsnotify_modify+0x4a/0x55
[ +0.000220] [<c10e48eb>] ? vfs_write+0xbb/0xc5
[ +0.000186] [<c106013f>] ? trace_hardirqs_on_caller+0x15f/0x17a
[ +0.000273] [<c130b6a8>] SyS_socketcall+0x13/0x15
[ +0.000200] [<c13ea628>] sysenter_do_call+0x12/0x12
The problematic code is bt_accept_dequeue() which calls the blocking
lock_sock() function. The simplest fix is to move setting
TASK_INTERRUPTIBLE after the call to bt_accept_dequeue(). This patch
makes this fix for our three socket types (L2CAP, RFCOMM & SCO).
Signed-off-by: Johan Hedberg <johan.hedberg@xxxxxxxxx>
---
Note: Due to my limited experience with waitqueues and playing with the
task state, this can be considered a rather naive approach to the
problem. However, the patch seems to work fine in practice and
effectively removes the warning in question.
net/bluetooth/l2cap_sock.c | 4 ++--
net/bluetooth/rfcomm/sock.c | 4 ++--
net/bluetooth/sco.c | 4 ++--
3 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 20206cd3acbc..8d723e6ae802 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -316,8 +316,6 @@ static int l2cap_sock_accept(struct socket *sock, struct socket *newsock,
/* Wait for an incoming connection. (wake-one). */
add_wait_queue_exclusive(sk_sleep(sk), &wait);
while (1) {
- set_current_state(TASK_INTERRUPTIBLE);
-
if (sk->sk_state != BT_LISTEN) {
err = -EBADFD;
break;
@@ -327,6 +325,8 @@ static int l2cap_sock_accept(struct socket *sock, struct socket *newsock,
if (nsk)
break;
+ set_current_state(TASK_INTERRUPTIBLE);
+
if (!timeo) {
err = -EAGAIN;
break;
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index d8a95755a8a8..8f492707f6d2 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -487,8 +487,6 @@ static int rfcomm_sock_accept(struct socket *sock, struct socket *newsock, int f
/* Wait for an incoming connection. (wake-one). */
add_wait_queue_exclusive(sk_sleep(sk), &wait);
while (1) {
- set_current_state(TASK_INTERRUPTIBLE);
-
if (sk->sk_state != BT_LISTEN) {
err = -EBADFD;
break;
@@ -498,6 +496,8 @@ static int rfcomm_sock_accept(struct socket *sock, struct socket *newsock, int f
if (nsk)
break;
+ set_current_state(TASK_INTERRUPTIBLE);
+
if (!timeo) {
err = -EAGAIN;
break;
diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
index 07ec7d23b843..ee9673e014cb 100644
--- a/net/bluetooth/sco.c
+++ b/net/bluetooth/sco.c
@@ -632,8 +632,6 @@ static int sco_sock_accept(struct socket *sock, struct socket *newsock, int flag
/* Wait for an incoming connection. (wake-one). */
add_wait_queue_exclusive(sk_sleep(sk), &wait);
while (1) {
- set_current_state(TASK_INTERRUPTIBLE);
-
if (sk->sk_state != BT_LISTEN) {
err = -EBADFD;
break;
@@ -643,6 +641,8 @@ static int sco_sock_accept(struct socket *sock, struct socket *newsock, int flag
if (ch)
break;
+ set_current_state(TASK_INTERRUPTIBLE);
+
if (!timeo) {
err = -EAGAIN;
break;
--
2.1.0
--
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