Hi Dan,
On Tue, Apr 07, 2020 at 04:55:59PM +0300, Dan Carpenter wrote:
> Hello Manivannan Sadhasivam,
>
> The patch 189ff97cca53: "bus: mhi: core: Add support for data
> transfer" from Feb 20, 2020, leads to the following static checker
> warning:
>
> drivers/bus/mhi/core/main.c:1153 mhi_queue_buf()
> error: double locked 'mhi_chan->lock' (orig line 1110)
>
> drivers/bus/mhi/core/main.c
> 1142 }
> 1143
> 1144 /* Toggle wake to exit out of M2 */
> 1145 mhi_cntrl->wake_toggle(mhi_cntrl);
> 1146
> 1147 if (mhi_chan->dir == DMA_TO_DEVICE)
> 1148 atomic_inc(&mhi_cntrl->pending_pkts);
> 1149
> 1150 if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl))) {
> 1151 unsigned long flags;
> 1152
> 1153 read_lock_irqsave(&mhi_chan->lock, flags);
> ^^^^^^^^^^^^^^^
> The caller is already holding this lock.
>
This function will be called from multiple places. It needs to have the
chan->lock on its own. I thought about dropping the lock in parse_xfer_event()
before calling this function but that won't really solve any issue since
read_locks are recursive and by doing so we are only making the static checkers
happy.
So I'd consider this bug report as false positive.
Thanks,
Mani
> 1154 mhi_ring_chan_db(mhi_cntrl, mhi_chan);
> 1155 read_unlock_irqrestore(&mhi_chan->lock, flags);
> 1156 }
> 1157
> 1158 read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
> 1159
> 1160 return 0;
> 1161 }
> 1162 EXPORT_SYMBOL_GPL(mhi_queue_buf);
>
> regards,
> dan carpenter
