linux-kernel - Re: [PATCH] bus: mhi: ep: Change state

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Message-ID: <59422195-28eb-4617-2529-5e997e5a7903@quicinc.com>
Date:   Mon, 23 Jan 2023 10:10:06 -0700
From:   Jeffrey Hugo <quic_jhugo@...cinc.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <mhi@...ts.linux.dev>
CC:     <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>, Dan Carpenter <error27@...il.com>
Subject: Re: [PATCH] bus: mhi: ep: Change state_lock to mutex

On 1/23/2023 12:50 AM, Manivannan Sadhasivam wrote:
> state_lock, the spinlock type is meant to protect race against concurrent
> MHI state transitions. In mhi_ep_set_m0_state(), while the state_lock is
> being held, the channels are resumed in mhi_ep_resume_channels() if the
> previous state was M3. This causes sleeping in atomic bug, since
> mhi_ep_resume_channels() use mutex internally.
> 
> Since the state_lock is supposed to be held throughout the state change,
> it is not ideal to drop the lock before calling mhi_ep_resume_channels().
> So to fix this issue, let's change the type of state_lock to mutex. This
> would also allow holding the lock throughout all state transitions thereby
> avoiding any potential race.
> 
> Cc: <stable@...r.kernel.org> # 5.19
> Fixes: e4b7b5f0f30a ("bus: mhi: ep: Add support for suspending and resuming channels")
> Reported-by: Dan Carpenter <error27@...il.com>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Looks sane.
Reviewed-by: Jeffrey Hugo <quic_jhugo@...cinc.com>