Messages in this thread | | | Date | Fri, 24 Nov 2023 15:34:03 +0530 | From | Manivannan Sadhasivam <> | Subject | Re: [PATCH v4 2/4] bus: mhi: host: Drop chan lock before queuing buffers |
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On Tue, Nov 14, 2023 at 01:27:39PM +0800, Qiang Yu wrote: > Ensure read and write locks for the channel are not taken in succession by > dropping the read lock from parse_xfer_event() such that a callback given > to client can potentially queue buffers and acquire the write lock in that > process. Any queueing of buffers should be done without channel read lock > acquired as it can result in multiple locks and a soft lockup. >
Is this patch trying to fix an existing issue in client drivers or a potential issue in the future drivers?
Even if you take care of disabled channels, "mhi_event->lock" acquired during mhi_mark_stale_events() can cause deadlock, since event lock is already held by mhi_ev_task().
I'd prefer not to open the window unless this patch is fixing a real issue.
- Mani
> Signed-off-by: Qiang Yu <quic_qianyu@quicinc.com> > --- > drivers/bus/mhi/host/main.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c > index 6c6d253..c4215b0 100644 > --- a/drivers/bus/mhi/host/main.c > +++ b/drivers/bus/mhi/host/main.c > @@ -642,6 +642,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl, > mhi_del_ring_element(mhi_cntrl, tre_ring); > local_rp = tre_ring->rp; > > + read_unlock_bh(&mhi_chan->lock); > + > /* notify client */ > mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result); > > @@ -667,6 +669,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl, > kfree(buf_info->cb_buf); > } > } > + > + read_lock_bh(&mhi_chan->lock); > } > break; > } /* CC_EOT */ > -- > 2.7.4 > >
-- மணிவண்ணன் சதாசிவம்
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