linux-kernel - Re: 3.7 RC1

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Message-ID: <20121024064135.GF20754@mwanda>
Date:	Wed, 24 Oct 2012 09:41:36 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	KY Srinivasan <kys@...rosoft.com>
Cc:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: Re: 3.7 RC1

On Tue, Oct 23, 2012 at 02:24:58PM +0000, KY Srinivasan wrote:
> 
> 
> > -----Original Message-----
> > From: Dan Carpenter [mailto:dan.carpenter@...cle.com]
> > Sent: Tuesday, October 23, 2012 1:47 AM
> > To: KY Srinivasan
> > Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> > devel@...uxdriverproject.org; olaf@...fle.de; apw@...onical.com;
> > jasowang@...hat.com
> > Subject: Re: 3.7 RC1
> > 
> > On Mon, Oct 22, 2012 at 04:37:45PM -0700, K. Y. Srinivasan wrote:
> > >
> > > While testing 3.7 RC1 I discovered that invoking the function
> > orderly_poweroff()
> > > from an interrupt context will trigger an ASSERT(). This was not the case till
> > > recently. The comment preceding the orderly_poweroff() function claims that
> > this
> > > function can be invoked from any context and in the current Hyper-V util driver,
> > > we support host-driven orderly shut down of the guest by invoking this
> > > orderly_poweroff() function in the context of the message callback. This code
> > has
> > > been working for a very long time and it is broken now. Is my assumption that
> > > orderly_poweroff() could be invoked from the interrupt context a wrong
> > assumption?
> > 
> > You can't call orderly_poweroff() from interrupt context.
> 
> Thanks Dan; I am curious  to understand the basis for your assertion.
> As I noted earlier  the documentation for this function clearly says it can
> be called from any context. Furthermore, __orderly_poweroff(), the helper
> function allocates memory with the GFP_ATOMIC flag set. Lastly, the behavior
> of orderly_poweroff() has been such that this function could be called from interrupt context
> for a very long time and something has changed now. For what it is worth, there are other users in
> the kernel (in 3.7 RC1) that are invoking the orderly_poweroff() function from interrupt
> context other than the Hyper-V shutdown handler:  fsl_hv_shutdown_isr() in drivers/virt/fsl_hypervisor.c.
> I suspect there are other users as well that have made this similar assumption.
> 

Aw crap.  I was wrong.  Sorry about that.

regards,
dan carpenter

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