This commit fixes the potential deadlock caused by the console Rx and Tx processing at the same time. Rx and Tx both take the console and tmfifo spinlock but in different order which causes potential deadlock. The fix is to use different tmfifo spinlock for Rx and Tx since they protect different resources and it's safe to split the lock.

Below is the reported call trace when copying/pasting large string in the console.

Rx: _raw_spin_lock_irqsave (hvc lock) __hvc_poll hvc_poll in_intr vring_interrupt mlxbf_tmfifo_rxtx_one_desc (tmfifo lock) mlxbf_tmfifo_rxtx mlxbf_tmfifo_work_rxtx Tx: _raw_spin_lock_irqsave (tmfifo lock) mlxbf_tmfifo_virtio_notify virtqueue_notify virtqueue_kick put_chars hvc_push hvc_write (hvc lock) ... do_tty_write tty_write

Fixes: 1357dfd7261f ("platform/mellanox: Add TmFifo driver for Mellanox BlueField Soc") Cc: stable@vger.kernel.org # 5.4+ Reviewed-by: David Woods dwoods@mellanox.com Signed-off-by: Liming Sun lsun@mellanox.com --- drivers/platform/mellanox/mlxbf-tmfifo.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c index 9a5c9fd..5739a966 100644 --- a/drivers/platform/mellanox/mlxbf-tmfifo.c +++ b/drivers/platform/mellanox/mlxbf-tmfifo.c @@ -149,7 +149,7 @@ struct mlxbf_tmfifo_irq_info { * @work: work struct for deferred process * @timer: background timer * @vring: Tx/Rx ring - * @spin_lock: spin lock + * @spin_lock: Tx/Rx spin lock * @is_ready: ready flag */ struct mlxbf_tmfifo { @@ -164,7 +164,7 @@ struct mlxbf_tmfifo { struct work_struct work; struct timer_list timer; struct mlxbf_tmfifo_vring *vring[2]; - spinlock_t spin_lock; /* spin lock */ + spinlock_t spin_lock[2]; /* spin lock */ bool is_ready; };

@@ -525,7 +525,7 @@ static void mlxbf_tmfifo_console_tx(struct mlxbf_tmfifo *fifo, int avail) writeq(*(u64 *)&hdr, fifo->tx_base + MLXBF_TMFIFO_TX_DATA);

/* Use spin-lock to protect the 'cons->tx_buf'. */ - spin_lock_irqsave(&fifo->spin_lock, flags); + spin_lock_irqsave(&fifo->spin_lock[0], flags);

while (size > 0) { addr = cons->tx_buf.buf + cons->tx_buf.tail; @@ -552,7 +552,7 @@ static void mlxbf_tmfifo_console_tx(struct mlxbf_tmfifo *fifo, int avail) } }

- spin_unlock_irqrestore(&fifo->spin_lock, flags); + spin_unlock_irqrestore(&fifo->spin_lock[0], flags); }

/* Rx/Tx one word in the descriptor buffer. */ @@ -731,9 +731,9 @@ static bool mlxbf_tmfifo_rxtx_one_desc(struct mlxbf_tmfifo_vring *vring, fifo->vring[is_rx] = NULL;

/* Notify upper layer that packet is done. */ - spin_lock_irqsave(&fifo->spin_lock, flags); + spin_lock_irqsave(&fifo->spin_lock[is_rx], flags); vring_interrupt(0, vring->vq); - spin_unlock_irqrestore(&fifo->spin_lock, flags); + spin_unlock_irqrestore(&fifo->spin_lock[is_rx], flags); }

mlxbf_tmfifo_desc_done: @@ -852,10 +852,10 @@ static bool mlxbf_tmfifo_virtio_notify(struct virtqueue *vq) * worker handler. */ if (vring->vdev_id == VIRTIO_ID_CONSOLE) { - spin_lock_irqsave(&fifo->spin_lock, flags); + spin_lock_irqsave(&fifo->spin_lock[0], flags); tm_vdev = fifo->vdev[VIRTIO_ID_CONSOLE]; mlxbf_tmfifo_console_output(tm_vdev, vring); - spin_unlock_irqrestore(&fifo->spin_lock, flags); + spin_unlock_irqrestore(&fifo->spin_lock[0], flags); } else if (test_and_set_bit(MLXBF_TM_TX_LWM_IRQ, &fifo->pend_events)) { return true; @@ -1189,7 +1189,8 @@ static int mlxbf_tmfifo_probe(struct platform_device *pdev) if (!fifo) return -ENOMEM;

- spin_lock_init(&fifo->spin_lock); + spin_lock_init(&fifo->spin_lock[0]); + spin_lock_init(&fifo->spin_lock[1]); INIT_WORK(&fifo->work, mlxbf_tmfifo_work_handler); mutex_init(&fifo->lock);