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From: Hoan Tran <hotran@apm.com>
Date: Wed, 9 Nov 2016 22:39:35 -0800
Message-ID: <CAFHUOYyJrFV4P9POyEx_fZ8c_AX-L0kHQrKqwqe4C2hKBu-Shg@mail.gmail.com>
Subject: Re: [PATCH v3] mailbox: PCC: Fix lockdep warning when request PCC channel
To: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        Prakash Prashanth <pprakash@codeaurora.org>
Cc: linux acpi <linux-acpi@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, Loc Ho <lho@apm.com>,
        Duc Dang <dhdang@apm.com>, Hoan Tran <hotran@apm.com>
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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);
> -
> -
> -/**
>   * pcc_send_data - Called from Mailbox Controller code. Used
>   *             here only to ring the channel doorbell. The PCC client
>   *             specific read/write is done in the client driver in
> --
> 1.9.1
>

Do you have any comments about this patch ?

Thanks
Hoan