linux-kernel - Re: [PATCH] PM: Prevent waiting forever on asynchronous suspend after abort

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Date:	Wed, 20 Jun 2012 10:58:25 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Mandeep Singh Baines <mandeep.baines@...il.com>
cc:	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Mandeep Singh Baines <msb@...omium.org>,
	<linux-pm@...r.kernel.org>, <stable@...nel.org>,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kevin Hilman <khilman@...com>,
	Colin Cross <ccross@...roid.com>,
	Sameer Nanda <snanda@...omium.org>,
	Olof Johansson <olofj@...omium.org>
Subject: Re: [PATCH] PM: Prevent waiting forever on asynchronous suspend
 after abort

On Tue, 19 Jun 2012, Mandeep Singh Baines wrote:

> __device_suspend() must always send a completion. Otherwise, parent
> devices will wait forever.
> 
> Commit 1e2ef05b, "PM: Limit race conditions between runtime PM and
> system sleep (v2)", introduced a regression by short-circuiting the
> complete_all() for certain error cases.
> 
> This patch fixes the bug by always signalling a completion.
> 
> Addresses http://crosbug.com/31972
> 
> Tested by injecting an abort via the following patch:
> 
> diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
> index a004db3..e5a6fce 100644
> --- a/drivers/usb/core/hcd-pci.c
> +++ b/drivers/usb/core/hcd-pci.c
> @@ -21,6 +21,7 @@
>  #include <linux/pci.h>
>  #include <linux/usb.h>
>  #include <linux/usb/hcd.h>
> +#include <linux/string.h>
> 
>  #include <asm/io.h>
>  #include <asm/irq.h>
> @@ -477,6 +478,8 @@ static int resume_common(struct device *dev, int event)
> 
>  static int hcd_pci_suspend(struct device *dev)
>  {
> +       if (!strcmp("0000:00:1d.3", dev_name(dev)))
> +               return -EBUSY;
>         return suspend_common(dev, device_may_wakeup(dev));
>  }

When you include one patch in front of another like this, doesn't it 
confuse the automatic tools?  You might end up getting both changes 
include in the final commit.  :-)

>  drivers/base/power/main.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index e0fb5b0..9cb845e 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1031,7 +1031,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
>  	dpm_wait_for_children(dev, async);
>  
>  	if (async_error)
> -		return 0;
> +		goto Complete;
>  
>  	pm_runtime_get_noresume(dev);
>  	if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
> @@ -1040,7 +1040,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
>  	if (pm_wakeup_pending()) {
>  		pm_runtime_put_sync(dev);
>  		async_error = -EBUSY;
> -		return 0;
> +		goto Complete;
>  	}
>  
>  	device_lock(dev);
> @@ -1097,6 +1097,8 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
>  	}
>  
>  	device_unlock(dev);
> +
> + Complete:
>  	complete_all(&dev->power.completion);
>  
>  	if (error) {

Otherwise this looks right to me.

Acked-by: Alan Stern <stern@...land.harvard.edu>

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