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    SubjectRe: [PATCH 2/3]: Staging: hv: Use native wait primitives
    On Tue, Feb 15, 2011 at 01:35:56PM +0000, KY Srinivasan wrote:
    >
    >
    > > -----Original Message-----
    > > From: Jiri Slaby [mailto:jirislaby@gmail.com]
    > > Sent: Tuesday, February 15, 2011 4:21 AM
    > > To: KY Srinivasan
    > > Cc: gregkh@suse.de; linux-kernel@vger.kernel.org;
    > > devel@linuxdriverproject.org; virtualization@lists.osdl.org
    > > Subject: Re: [PATCH 2/3]: Staging: hv: Use native wait primitives
    > >
    > > On 02/11/2011 06:59 PM, K. Y. Srinivasan wrote:
    > > > In preperation for getting rid of the osd layer; change
    > > > the code to use native wait interfaces. As part of this,
    > > > fixed the buggy implementation in the osd_wait_primitive
    > > > where the condition was cleared potentially after the
    > > > condition was signalled.
    > > ...
    > > > @@ -566,7 +567,11 @@ int vmbus_establish_gpadl(struct vmbus_channel
    > > *channel, void *kbuffer,
    > > >
    > > > }
    > > > }
    > > > - osd_waitevent_wait(msginfo->waitevent);
    > > > + wait_event_timeout(msginfo->waitevent,
    > > > + msginfo->wait_condition,
    > > > + msecs_to_jiffies(1000));
    > > > + BUG_ON(msginfo->wait_condition == 0);
    > >
    > > The added BUG_ONs all over the code look scary. These shouldn't be
    > > BUG_ONs at all. You should maybe warn and bail out, but not kill the
    > > whole machine.
    >
    > This is Linux code running as a guest on a Windows host; and so the guest cannot
    > tolerate a failure of the host. In the cases where I have chosen to BUG_ON, there
    > is no reasonable recovery possible when the host is non-functional (as determined
    > by a non-responsive host).

    If you have a non-responsive host, wouldn't that imply that this guest
    code wouldn't run at all? :)

    Having BUG_ON() in drivers is not a good idea either way. Please remove
    these in future patches.

    > > And looking at the code, more appropriate would be completion instead of
    > > wait events.
    > >
    > > And msecs_to_jiffies(1000) == HZ.
    >
    > Agreed. In this first round of cleanup, I chose to keep the primitives
    > as they were in osd.c. Greg, if it is ok with you, I will send you a
    > patch that fixes these issues on top of the patches I have already
    > sent.

    Yes, that is fine.

    thanks,

    greg k-h

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