On Tue, Feb 01, 2022 at 05:15:40PM +0000, Daniel Thompson wrote: > On Sat, Jan 29, 2022 at 10:56:30AM +0800, Jia-Ju Bai wrote: > > Hello, > > > > My static analysis tool reports a possible deadlock in the mhi driver in > > Linux 5.10: > > > > mhi_async_power_up() > > mutex_lock(&mhi_cntrl->pm_mutex); --> Line 933 (Lock A) > > wait_event_timeout(mhi_cntrl->state_event, ...) --> Line 985 (Wait X) > > mutex_unlock(&mhi_cntrl->pm_mutex); --> Line 1040 (Unlock A) > > > > mhi_pm_disable_transition() > > mutex_lock(&mhi_cntrl->pm_mutex); --> Line 463 (Lock A) > > wake_up_all(&mhi_cntrl->state_event); --> Line 474 (Wake X) > > mutex_unlock(&mhi_cntrl->pm_mutex); --> Line 524 (Unlock A) > > wake_up_all(&mhi_cntrl->state_event); --> Line 526 (Wake X) > > > > When mhi_async_power_up() is executed, "Wait X" is performed by holding > > "Lock A". If mhi_pm_disable_transition() is concurrently executed at this > > time, "Wake X" cannot be performed to wake up "Wait X" in > > mhi_async_power_up(), because "Lock A" is already hold by > > mhi_async_power_up(), causing a possible deadlock. > > I find that "Wait X" is performed with a timeout, to relieve the possible > > deadlock; but I think this timeout can cause inefficient execution. > > > > I am not quite sure whether this possible problem is real and how to fix it > > if it is real. > > Any feedback would be appreciated, thanks :) > > Interesting find but I think it would be better to run your tool > against more recent kernels to confirm any problem reports. In this > case the code you mention looks like it was removed in v5.17-rc1 > (and should eventually make its way to the stable kernels too). > Hmm, looks like the commit didn't apply cleanly to 5.10: https://www.spinics.net/lists/stable/msg526754.html Let send the fix up version. Thanks, Mani > > Daniel.
