From: Dave Airlie airlied@redhat.com
With drm-next, we can get a backtrace like below, this is due to the callback checking the txmsg state taking the mutex, which can cause a sleep inside a sleep,
Fix this my creating a spinlock protecting the txmsg state and locking it in appropriate places.
: ------------[ cut here ]------------ : WARNING: CPU: 3 PID: 252 at kernel/sched/core.c:7300 __might_sleep+0xbd/0xd0() : do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff810db8ad>] prepare_to_wait_event+0x5d/0x110 : Modules linked in: i915 i2c_algo_bit drm_kms_helper drm e1000e ptp pps_core i2c_core video : CPU: 3 PID: 252 Comm: kworker/3:2 Not tainted 3.19.0-rc5+ #18 : Hardware name: LENOVO 20ARS25701/20ARS25701, BIOS GJET72WW (2.22 ) 02/21/2014 : Workqueue: events_long drm_dp_mst_link_probe_work [drm_kms_helper] : ffffffff81a4027c ffff88030a763af8 ffffffff81752699 0000000000000000 : ffff88030a763b48 ffff88030a763b38 ffffffff810974ca ffff88030a763b38 : ffffffff81a41123 000000000000026d 0000000000000000 0000000000000fa0 : Call Trace: : [<ffffffff81752699>] dump_stack+0x4c/0x65 : [<ffffffff810974ca>] warn_slowpath_common+0x8a/0xc0 : [<ffffffff81097546>] warn_slowpath_fmt+0x46/0x50 : [<ffffffff810db8ad>] ? prepare_to_wait_event+0x5d/0x110 : [<ffffffff810db8ad>] ? prepare_to_wait_event+0x5d/0x110 : [<ffffffff810bdaad>] __might_sleep+0xbd/0xd0 : [<ffffffff817566de>] mutex_lock_nested+0x2e/0x3e0 : [<ffffffff810db8e8>] ? prepare_to_wait_event+0x98/0x110 : [<ffffffffa00e43d7>] drm_dp_mst_wait_tx_reply+0xa7/0x220 [drm_kms_helper] : [<ffffffff810db790>] ? wait_woken+0xc0/0xc0 : [<ffffffffa00e6401>] drm_dp_send_link_address+0x61/0x240 [drm_kms_helper] : [<ffffffff810b1aaf>] ? process_one_work+0x14f/0x530 : [<ffffffffa00e6abd>] drm_dp_check_and_send_link_address+0x8d/0xa0 [drm_kms_helper] : [<ffffffffa00e6aec>] drm_dp_mst_link_probe_work+0x1c/0x20 [drm_kms_helper] : [<ffffffff810b1b26>] process_one_work+0x1c6/0x530 : [<ffffffff810b1aaf>] ? process_one_work+0x14f/0x530 : [<ffffffff810b224b>] worker_thread+0x6b/0x490 : [<ffffffff810b21e0>] ? rescuer_thread+0x350/0x350 : [<ffffffff810b73ea>] kthread+0x10a/0x120 : [<ffffffff8175a800>] ? _raw_spin_unlock_irq+0x30/0x50 : [<ffffffff810b72e0>] ? kthread_create_on_node+0x220/0x220 : [<ffffffff8175b1fc>] ret_from_fork+0x7c/0xb0 : [<ffffffff810b72e0>] ? kthread_create_on_node+0x220/0x220 : ---[ end trace bb11c9634a7217c6 ]---
Signed-off-by: Dave Airlie airlied@redhat.com --- drivers/gpu/drm/drm_dp_mst_topology.c | 15 +++++++++++++-- include/drm/drm_dp_mst_helper.h | 4 +++- 2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 9a5b687..07662ae 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -733,10 +733,10 @@ static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_sideband_msg_tx *txmsg) { bool ret; - mutex_lock(&mgr->qlock); + spin_lock(&mgr->state_lock); ret = (txmsg->state == DRM_DP_SIDEBAND_TX_RX || txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT); - mutex_unlock(&mgr->qlock); + spin_unlock(&mgr->state_lock); return ret; }
@@ -750,6 +750,7 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, check_txmsg_state(mgr, txmsg), (4 * HZ)); mutex_lock(&mstb->mgr->qlock); + spin_lock(&mgr->state_lock); if (ret > 0) { if (txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT) { ret = -EIO; @@ -773,6 +774,7 @@ static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb, } } out: + spin_unlock(&mgr->state_lock); mutex_unlock(&mgr->qlock);
return ret; @@ -1318,10 +1320,12 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr));
+ spin_lock(&mgr->state_lock); if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) { txmsg->seqno = -1; txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND; } + spin_unlock(&mgr->state_lock);
/* make hdr from dst mst - for replies use seqno otherwise assign one */ @@ -1357,7 +1361,9 @@ static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
txmsg->cur_offset += tosend; if (txmsg->cur_offset == txmsg->cur_len) { + spin_lock(&mgr->state_lock); txmsg->state = DRM_DP_SIDEBAND_TX_SENT; + spin_unlock(&mgr->state_lock); return 1; } return 0; @@ -1386,7 +1392,9 @@ static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr) list_del(&txmsg->next); if (txmsg->seqno != -1) txmsg->dst->tx_slots[txmsg->seqno] = NULL; + spin_lock(&mgr->state_lock); txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT; + spin_unlock(&mgr->state_lock); wake_up(&mgr->tx_waitq); } if (list_empty(&mgr->tx_msg_downq)) { @@ -2083,7 +2091,9 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr) drm_dp_put_mst_branch_device(mstb);
mutex_lock(&mgr->qlock); + spin_lock(&mgr->state_lock); txmsg->state = DRM_DP_SIDEBAND_TX_RX; + spin_unlock(&mgr->state_lock); mstb->tx_slots[slot] = NULL; mutex_unlock(&mgr->qlock);
@@ -2633,6 +2643,7 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr, mutex_init(&mgr->lock); mutex_init(&mgr->qlock); mutex_init(&mgr->payload_lock); + spin_lock_init(&mgr->state_lock); INIT_LIST_HEAD(&mgr->tx_msg_upq); INIT_LIST_HEAD(&mgr->tx_msg_downq); INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work); diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 00c1da9..7cd1735 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -445,8 +445,10 @@ struct drm_dp_mst_topology_mgr {
/* messages to be transmitted */ /* qlock protects the upq/downq and in_progress, - the mstb tx_slots and txmsg->state once they are queued */ + the mstb tx_slots once they are queued */ struct mutex qlock; + /* state lock protects txmsg->state */ + spinlock_t state_lock; struct list_head tx_msg_downq; struct list_head tx_msg_upq; bool tx_down_in_progress;