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From: Hoan Tran <hotran@apm.com>
Date: Mon, 14 Nov 2016 11:21:25 -0800
Message-ID: <CAFHUOYwwq2p_OmcBhJ388r1DoK9JVuv0UfCRR8tsAFjGkCEBTQ@mail.gmail.com>
Subject: Re: [PATCH v3] mailbox: PCC: Fix lockdep warning when request PCC channel
To: "Prakash, Prashanth" <pprakash@codeaurora.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        linux acpi <linux-acpi@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, Loc Ho <lho@apm.com>,
        Duc Dang <dhdang@apm.com>
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Hi,

On Sun, Nov 13, 2016 at 11:44 AM, Prakash, Prashanth
<pprakash@codeaurora.org> wrote:
> HI Hoan,
>
> On 11/9/2016 11:39 PM, Hoan Tran wrote:
>> Hi All,
>>
>> On Thu, Oct 27, 2016 at 3:34 PM, Hoan Tran <hotran@apm.com> wrote:
>>> This patch fixes the lockdep warning below
>>>
>>> [    7.229767] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
>>> [    7.229776] ------------[ cut here ]------------
>>> [    7.229787] WARNING: CPU: 1 PID: 1 at linux-next/kernel/locking/lockdep.c:2876 loc
>>> kdep_trace_alloc+0xe0/0xf0
>>> [    7.229790] Modules linked in:
>>> [    7.229793]
>>> [    7.229798] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.8.0-11756-g86c5152 #46
>>> ...
>>> [    7.229900] Call trace:
>>> [    7.229903] Exception stack(0xffff8007da837890 to 0xffff8007da8379c0)
>>> [    7.229906] 7880:                                   ffff8007da834000 0001000000000000
>>> [    7.229909] 78a0: ffff8007da837a70 ffff0000081111a0 00000000600000c5 000000000000003d
>>> [    7.229912] 78c0: 9374bc6a7f3c7832 0000000000381878 ffff000009db7ab8 000000000000002f
>>> [    7.229915] 78e0: ffff00000811aabc ffff000008be2548 ffff8007da837990 ffff00000811adf8
>>> [    7.229918] 7900: ffff8007da834000 00000000024080c0 00000000000000c0 ffff000009021000
>>> [    7.229921] 7920: 0000000000000000 0000000000000000 ffff000008c8f7c8 ffff8007da579810
>>> [    7.229923] 7940: 000000000000002f ffff8007da858000 0000000000000000 0000000000000001
>>> [    7.229926] 7960: 0000000000000001 0000000000000000 ffff00000811a468 0000000000000002
>>> [    7.229929] 7980: 656c62617369645f 0000000000038187 00000000000000ee ffff8007da837850
>>> [    7.229932] 79a0: ffff000009db50c0 ffff000009db569d 0000000000000006 ffff000089db568f
>>> [    7.229936] [<ffff0000081111a0>] lockdep_trace_alloc+0xe0/0xf0
>>> [    7.229940] [<ffff0000081f4950>] __kmalloc_track_caller+0x50/0x250
>>> [    7.229945] [<ffff00000857c088>] devres_alloc_node+0x28/0x60
>>> [    7.229949] [<ffff0000081220e0>] devm_request_threaded_irq+0x50/0xe0
>>> [    7.229955] [<ffff0000087e6220>] pcc_mbox_request_channel+0x110/0x170
>>> [    7.229960] [<ffff0000084b2660>] acpi_cppc_processor_probe+0x264/0x414
>>> [    7.229963] [<ffff0000084ae9f4>] __acpi_processor_start+0x28/0xa0
>>> [    7.229966] [<ffff0000084aeab0>] acpi_processor_start+0x44/0x54
>>> [    7.229970] [<ffff00000857897c>] driver_probe_device+0x1fc/0x2b0
>>> [    7.229974] [<ffff000008578ae4>] __driver_attach+0xb4/0xc0
>>> [    7.229977] [<ffff00000857683c>] bus_for_each_dev+0x5c/0xa0
>>> [    7.229980] [<ffff000008578110>] driver_attach+0x20/0x30
>>> [    7.229983] [<ffff000008577c20>] bus_add_driver+0x110/0x230
>>> [    7.229987] [<ffff000008579320>] driver_register+0x60/0x100
>>> [    7.229991] [<ffff000008d478b8>] acpi_processor_driver_init+0x2c/0xb0
>>> [    7.229996] [<ffff000008083168>] do_one_initcall+0x38/0x130
>>> [    7.230000] [<ffff000008d20d6c>] kernel_init_freeable+0x210/0x2b4
>>> [    7.230004] [<ffff000008945d90>] kernel_init+0x10/0x110
>>> [    7.230007] [<ffff000008082e80>] ret_from_fork+0x10/0x50
>>>
>>> It's because the spinlock inside pcc_mbox_request_channel() is
>>> kept too long. This patch releases spinlock before request_irq()
>>> and free_irq() to fix this issue  as spinlock is only needed to
>>> protect the channel data.
>>>
>>> Signed-off-by: Hoan Tran <hotran@apm.com>
>>> ---
>>> v3
>>>  * Free mailbox irq before reset the channel data
>>>  * Free channel if it fails to request the mailbox irq
>>>
>>> v2
>>>  * Release spinlock before request_irq() and free_irq() instead of
>>> using mutex
>>>
>>>
>>>  drivers/mailbox/pcc.c | 70 +++++++++++++++++++++++++--------------------------
>>>  1 file changed, 35 insertions(+), 35 deletions(-)
>>>
>>> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
>>> index 08c87fa..4b2f061 100644
>>> --- a/drivers/mailbox/pcc.c
>>> +++ b/drivers/mailbox/pcc.c
>>> @@ -224,6 +224,38 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
>>>  }
>>>
>>>  /**
>>> + * pcc_mbox_free_channel - Clients call this to free their Channel.
>>> + *
>>> + * @chan: Pointer to the mailbox channel as returned by
>>> + *             pcc_mbox_request_channel()
>>> + */
>>> +void pcc_mbox_free_channel(struct mbox_chan *chan)
>>> +{
>>> +       u32 id = chan - pcc_mbox_channels;
>>> +       unsigned long flags;
>>> +
>>> +       if (!chan || !chan->cl)
>>> +               return;
>>> +
>>> +       if (id >= pcc_mbox_ctrl.num_chans) {
>>> +               pr_debug("pcc_mbox_free_channel: Invalid mbox_chan passed\n");
>>> +               return;
>>> +       }
>>> +
>>> +       if (pcc_doorbell_irq[id] > 0)
>>> +               devm_free_irq(chan->mbox->dev, pcc_doorbell_irq[id], chan);
>>> +
>>> +       spin_lock_irqsave(&chan->lock, flags);
>>> +       chan->cl = NULL;
>>> +       chan->active_req = NULL;
>>> +       if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
>>> +               chan->txdone_method = TXDONE_BY_POLL;
>>> +
>>> +       spin_unlock_irqrestore(&chan->lock, flags);
>>> +}
>>> +EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
>>> +
>>> +/**
>>>   * pcc_mbox_request_channel - PCC clients call this function to
>>>   *             request a pointer to their PCC subspace, from which they
>>>   *             can get the details of communicating with the remote.
>>> @@ -267,6 +299,8 @@ struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
>>>         if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
>>>                 chan->txdone_method |= TXDONE_BY_ACK;
>>>
>>> +       spin_unlock_irqrestore(&chan->lock, flags);
>>> +
>>>         if (pcc_doorbell_irq[subspace_id] > 0) {
>>>                 int rc;
>>>
>>> @@ -275,50 +309,16 @@ struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
>>>                 if (unlikely(rc)) {
>>>                         dev_err(dev, "failed to register PCC interrupt %d\n",
>>>                                 pcc_doorbell_irq[subspace_id]);
>>> +                       pcc_mbox_free_channel(chan);
>>>                         chan = ERR_PTR(rc);
>>>                 }
>>>         }
>>>
>>> -       spin_unlock_irqrestore(&chan->lock, flags);
>>> -
>>>         return chan;
>>>  }
>>>  EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
>>>
>>>  /**
>>> - * pcc_mbox_free_channel - Clients call this to free their Channel.
>>> - *
>>> - * @chan: Pointer to the mailbox channel as returned by
>>> - *             pcc_mbox_request_channel()
>>> - */
>>> -void pcc_mbox_free_channel(struct mbox_chan *chan)
>>> -{
>>> -       u32 id = chan - pcc_mbox_channels;
>>> -       unsigned long flags;
>>> -
>>> -       if (!chan || !chan->cl)
>>> -               return;
>>> -
>>> -       if (id >= pcc_mbox_ctrl.num_chans) {
>>> -               pr_debug("pcc_mbox_free_channel: Invalid mbox_chan passed\n");
>>> -               return;
>>> -       }
>>> -
>>> -       spin_lock_irqsave(&chan->lock, flags);
>>> -       chan->cl = NULL;
>>> -       chan->active_req = NULL;
>>> -       if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
>>> -               chan->txdone_method = TXDONE_BY_POLL;
>>> -
>>> -       if (pcc_doorbell_irq[id] > 0)
>>> -               devm_free_irq(chan->mbox->dev, pcc_doorbell_irq[id], chan);
>>> -
>>> -       spin_unlock_irqrestore(&chan->lock, flags);
>>> -}
>>> -EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
> Instead of completely relocating an exported function within the file, I think
> we can just include the "pcc.h" header, which makes it a little easier to review.

I just sent out another patch which included pcc.h instead.

Thanks
Hoan

>
> Otherwise, the control flow looks ok now.
>
> --
> Thanks,
> Prashanth