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From: richardcochran@gmail.com (Richard Cochran)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 4/4] net: macb: Add hardware PTP support
Date: Wed, 7 Jun 2017 15:28:17 +0200	[thread overview]
Message-ID: <20170607132817.GA28329@localhost.localdomain> (raw)
In-Reply-To: <BN3PR07MB2516A47C2CFEB58BCFFB2C46C9C80@BN3PR07MB2516.namprd07.prod.outlook.com>

On Wed, Jun 07, 2017 at 11:13:36AM +0000, Rafal Ozieblo wrote:
> Please look at following call-stack:
> 
> 1. macb_interrupt()   // spin_lock(&bp->lock) is taken
> 2. macb_tx_interrupt()
> 3. macb_handle_txtstamp()
> 4. skb_tstamp_tx()
> 5. __skb_tstamp_tx()
> 6. skb_may_tx_timestamp()
> 7. read_lock_bh() // second lock is taken

Well, you can always drop the lock, or postpone the call to
skb_tstamp_tx() until after the spin lock is released...

> I know that those are different locks and different types. But this could lead 
> to deadlocks. This is the reason of warning I could see.

Can you please post the lockdep splat?

Thanks,
Richard

WARNING: multiple messages have this Message-ID (diff)
From: Richard Cochran <richardcochran-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Rafal Ozieblo <rafalo-vna1KIf7WgpBDgjK7y7TUQ@public.gmane.org>
Cc: David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
	"nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org"
	<nicolas.ferre-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>,
	"netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org"
	<linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>,
	"harini.katakam-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org"
	<harini.katakam-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org>,
	"andrei.pistirica-UWL1GkI3JZL3oGB3hsPCZA@public.gmane.org"
	<andrei.pistirica-UWL1GkI3JZL3oGB3hsPCZA@public.gmane.org>
Subject: Re: [PATCH v2 4/4] net: macb: Add hardware PTP support
Date: Wed, 7 Jun 2017 15:28:17 +0200	[thread overview]
Message-ID: <20170607132817.GA28329@localhost.localdomain> (raw)
In-Reply-To: <BN3PR07MB2516A47C2CFEB58BCFFB2C46C9C80-EldUQEzkDQfxGZiqM5fOI+FPX92sqiQdvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>

On Wed, Jun 07, 2017 at 11:13:36AM +0000, Rafal Ozieblo wrote:
> Please look at following call-stack:
> 
> 1. macb_interrupt()   // spin_lock(&bp->lock) is taken
> 2. macb_tx_interrupt()
> 3. macb_handle_txtstamp()
> 4. skb_tstamp_tx()
> 5. __skb_tstamp_tx()
> 6. skb_may_tx_timestamp()
> 7. read_lock_bh() // second lock is taken

Well, you can always drop the lock, or postpone the call to
skb_tstamp_tx() until after the spin lock is released...

> I know that those are different locks and different types. But this could lead 
> to deadlocks. This is the reason of warning I could see.

Can you please post the lockdep splat?

Thanks,
Richard

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WARNING: multiple messages have this Message-ID (diff)
From: Richard Cochran <richardcochran@gmail.com>
To: Rafal Ozieblo <rafalo@cadence.com>
Cc: David Miller <davem@davemloft.net>,
	"nicolas.ferre@atmel.com" <nicolas.ferre@atmel.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"harini.katakam@xilinx.com" <harini.katakam@xilinx.com>,
	"andrei.pistirica@microchip.com" <andrei.pistirica@microchip.com>
Subject: Re: [PATCH v2 4/4] net: macb: Add hardware PTP support
Date: Wed, 7 Jun 2017 15:28:17 +0200	[thread overview]
Message-ID: <20170607132817.GA28329@localhost.localdomain> (raw)
In-Reply-To: <BN3PR07MB2516A47C2CFEB58BCFFB2C46C9C80@BN3PR07MB2516.namprd07.prod.outlook.com>

On Wed, Jun 07, 2017 at 11:13:36AM +0000, Rafal Ozieblo wrote:
> Please look at following call-stack:
> 
> 1. macb_interrupt()   // spin_lock(&bp->lock) is taken
> 2. macb_tx_interrupt()
> 3. macb_handle_txtstamp()
> 4. skb_tstamp_tx()
> 5. __skb_tstamp_tx()
> 6. skb_may_tx_timestamp()
> 7. read_lock_bh() // second lock is taken

Well, you can always drop the lock, or postpone the call to
skb_tstamp_tx() until after the spin lock is released...

> I know that those are different locks and different types. But this could lead 
> to deadlocks. This is the reason of warning I could see.

Can you please post the lockdep splat?

Thanks,
Richard

  reply	other threads:[~2017-06-07 13:28 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-02 14:23 [PATCH v2 0/4] PTP support for macb driver Rafal Ozieblo
2017-06-02 14:23 ` Rafal Ozieblo
2017-06-02 14:23 ` Rafal Ozieblo
2017-06-02 14:26 ` [PATCH v2 1/4] net: macb: Add support for PTP timestamps in DMA descriptors Rafal Ozieblo
2017-06-02 14:26   ` Rafal Ozieblo
2017-06-02 14:26   ` Rafal Ozieblo
2017-06-02 14:27 ` [PATCH v2 2/4] net: macb: Add tsu_clk to device tree Rafal Ozieblo
2017-06-02 14:27   ` Rafal Ozieblo
2017-06-02 14:27   ` Rafal Ozieblo
     [not found] ` <1496413439-12900-1-git-send-email-rafalo-vna1KIf7WgpBDgjK7y7TUQ@public.gmane.org>
2017-06-02 14:27   ` [PATCH v2 3/4] net: macb: macb.c changed to macb_main.c Rafal Ozieblo
2017-06-02 14:27     ` Rafal Ozieblo
2017-06-02 14:27     ` Rafal Ozieblo
2017-06-06 18:39     ` Richard Cochran
2017-06-06 18:39       ` Richard Cochran
2017-06-06 18:39       ` Richard Cochran
2017-06-06 19:00       ` David Miller
2017-06-06 19:00         ` David Miller
2017-06-06 19:00         ` David Miller
2017-06-06 20:22         ` Richard Cochran
2017-06-06 20:22           ` Richard Cochran
2017-06-06 20:22           ` Richard Cochran
2017-06-02 14:28 ` [PATCH v2 4/4] net: macb: Add hardware PTP support Rafal Ozieblo
2017-06-02 14:28   ` Rafal Ozieblo
2017-06-02 14:28   ` Rafal Ozieblo
2017-06-04 20:55   ` Richard Cochran
2017-06-04 20:55     ` Richard Cochran
2017-06-04 20:55     ` Richard Cochran
2017-06-06  8:54     ` Rafal Ozieblo
2017-06-06  8:54       ` Rafal Ozieblo
2017-06-06 18:36       ` Richard Cochran
2017-06-06 18:36         ` Richard Cochran
2017-06-06 18:36         ` Richard Cochran
2017-06-06 18:33   ` Richard Cochran
2017-06-06 18:33     ` Richard Cochran
2017-06-07 11:13     ` Rafal Ozieblo
2017-06-07 11:13       ` Rafal Ozieblo
2017-06-07 11:13       ` Rafal Ozieblo
2017-06-07 13:28       ` Richard Cochran [this message]
2017-06-07 13:28         ` Richard Cochran
2017-06-07 13:28         ` Richard Cochran
2017-06-08 12:48         ` Rafal Ozieblo
2017-06-08 12:48           ` Rafal Ozieblo

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