Hi Brian, > -----Original Message----- > From: Brian Norris [mailto:briannorris@xxxxxxxxxxxx] > Sent: Friday, January 26, 2018 12:30 AM > To: Ganapathi Bhat > Cc: linux-wireless@xxxxxxxxxxxxxxx; Cathy Luo; Xinming Hu; Zhiyuan Yang; > James Cao; Mangesh Malusare; Shrenik Shikhare > Subject: [EXT] Re: [PATCH 1/2] mwifiex: schedule rx_work on RX interrupt for > USB > > External Email > > ---------------------------------------------------------------------- > On Mon, Jan 22, 2018 at 08:34:56PM +0530, Ganapathi Bhat wrote: > > From: Shrenik Shikhare <shrenik@xxxxxxxxxxx> > > > > There is race for data_received flag between main thread and RX data > > interrupt(mwifiex_usb_rx_complete()): > > 1. USB received an RX data interrupt, set data_received flag 2. main > > thread checks data_received, if set queues rx_work > > Stop right there. > > There is a flag, data_received, and as you say, you are setting it one thread, > and reading it in another thread (and later clearing it; step #5). Where is the > locking? There is none. Therefore, you have a data race. Yes. We missed it. We will add the locking and send it in v3. > > You are not resolving any locking problems here, so you're not really solving > the entire problem. > > Brian > > > 3. rx worker thread independently start processing rx_data_q 4. rx > > work exits (once rx_data_q is empty) 5. main thread resets the > > data_received flag(after #2) 6. Now at the corner case there will be > > high RX data interrupts between #4 and #5 7. Driver stops submitting > > URBs to firmware, once rx_pending exceeds HIGH_RX_PENDING 8. The > flag > > data_received(cleared in #5) will remain unset since there will be no > > interrupts from firmware to set it(after #7) > > > > Above scenario causes RX stall in driver, which will finally result in > > command/TX timeouts in firmware. > > > > As a fix, queue rx_work directly in mwifiex_usb_rx_complete() > > callback, instead in the main thread. This removes dependency of RX > > processing on data_received flag. > > > > Signed-off-by: Cathy Luo <cluo@xxxxxxxxxxx> > > Signed-off-by: Ganapathi Bhat <gbhat@xxxxxxxxxxx> > > --- > > drivers/net/wireless/marvell/mwifiex/main.c | 7 ++++--- > > drivers/net/wireless/marvell/mwifiex/main.h | 1 + > > drivers/net/wireless/marvell/mwifiex/usb.c | 2 ++ > > 3 files changed, 7 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/net/wireless/marvell/mwifiex/main.c > > b/drivers/net/wireless/marvell/mwifiex/main.c > > index 12e7399..6e6e1a7 100644 > > --- a/drivers/net/wireless/marvell/mwifiex/main.c > > +++ b/drivers/net/wireless/marvell/mwifiex/main.c > > @@ -171,7 +171,7 @@ void mwifiex_queue_main_work(struct > > mwifiex_adapter *adapter) } > > EXPORT_SYMBOL_GPL(mwifiex_queue_main_work); > > > > -static void mwifiex_queue_rx_work(struct mwifiex_adapter *adapter) > > +void mwifiex_queue_rx_work(struct mwifiex_adapter *adapter) > > { > > unsigned long flags; > > > > @@ -183,6 +183,7 @@ static void mwifiex_queue_rx_work(struct > mwifiex_adapter *adapter) > > queue_work(adapter->rx_workqueue, &adapter->rx_work); > > } > > } > > +EXPORT_SYMBOL_GPL(mwifiex_queue_rx_work); > > > > static int mwifiex_process_rx(struct mwifiex_adapter *adapter) { @@ > > -283,10 +284,10 @@ int mwifiex_main_process(struct mwifiex_adapter > *adapter) > > mwifiex_process_hs_config(adapter); > > if (adapter->if_ops.process_int_status) > > adapter- > >if_ops.process_int_status(adapter); > > + if (adapter->rx_work_enabled && adapter- > >data_received) > > + mwifiex_queue_rx_work(adapter); > > } > > > > - if (adapter->rx_work_enabled && adapter->data_received) > > - mwifiex_queue_rx_work(adapter); > > > > /* Need to wake up the card ? */ > > if ((adapter->ps_state == PS_STATE_SLEEP) && diff --git > > a/drivers/net/wireless/marvell/mwifiex/main.h > > b/drivers/net/wireless/marvell/mwifiex/main.h > > index 6b5539b..66ba95c 100644 > > --- a/drivers/net/wireless/marvell/mwifiex/main.h > > +++ b/drivers/net/wireless/marvell/mwifiex/main.h > > @@ -1667,6 +1667,7 @@ u8 mwifiex_adjust_data_rate(struct > > mwifiex_private *priv, void mwifiex_upload_device_dump(struct > > mwifiex_adapter *adapter); void *mwifiex_alloc_dma_align_buf(int > > rx_len, gfp_t flags); void mwifiex_queue_main_work(struct > > mwifiex_adapter *adapter); > > +void mwifiex_queue_rx_work(struct mwifiex_adapter *adapter); > > int mwifiex_get_wakeup_reason(struct mwifiex_private *priv, u16 action, > > int cmd_type, > > struct mwifiex_ds_wakeup_reason > *wakeup_reason); diff --git > > a/drivers/net/wireless/marvell/mwifiex/usb.c > > b/drivers/net/wireless/marvell/mwifiex/usb.c > > index 4bc2448..d20fda1 100644 > > --- a/drivers/net/wireless/marvell/mwifiex/usb.c > > +++ b/drivers/net/wireless/marvell/mwifiex/usb.c > > @@ -144,6 +144,8 @@ static int mwifiex_usb_recv(struct mwifiex_adapter > *adapter, > > skb_queue_tail(&adapter->rx_data_q, skb); > > adapter->data_received = true; > > atomic_inc(&adapter->rx_pending); > > + if (adapter->rx_work_enabled) > > + mwifiex_queue_rx_work(adapter); > > break; > > default: > > mwifiex_dbg(adapter, ERROR, > > -- > > 1.9.1 > > Regards, Ganapathi
