linux-kernel - RE: [PATCH 1/1] hv: Use only one receive buffer and kmalloc on initialize

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Message-ID: <8AFC7968D54FB448A30D8F38F259C5622C0BB71F@TK5EX14MBXC116.redmond.corp.microsoft.com>
Date:	Mon, 13 Dec 2010 19:31:42 +0000
From:	Hank Janssen <hjanssen@...rosoft.com>
To:	Greg KH <greg@...ah.com>
CC:	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: RE: [PATCH 1/1] hv: Use only one receive buffer and kmalloc on
 initialize



> -----Original Message-----
> From: Greg KH [mailto:greg@...ah.com]
> Sent: Monday, December 13, 2010 10:35 AM
> > ---
> >  drivers/staging/hv/hv_utils.c |   68 +++++++++++++++++++------------------
> ---
> >  1 files changed, 32 insertions(+), 36 deletions(-)
> >
> > diff --git a/drivers/staging/hv/hv_utils.c
> > b/drivers/staging/hv/hv_utils.c index 53e1e29..4ed4ab8 100644
> > --- a/drivers/staging/hv/hv_utils.c
> > +++ b/drivers/staging/hv/hv_utils.c
> > @@ -38,12 +38,15 @@
> >  #include "vmbus_api.h"
> >  #include "utils.h"
> >
> > +/*
> > + * Buffer used to receive packets from Hyper-V  */ static u8
> > +*chan_buf;
> 
> One buffer is nicer, yes, but what's controlling access to this buffer?
> You use it in multiple functions, and what's to say those functions can't be
> called at the same time on different cpus?  So, shouldn't you either have
> some locking for access to the buffer, or have a per-function buffer instead?
> 
> And if you have a per-function buffer, again, you might need to control
> access to it as the functions could be called multiple times at the same time,
> right?
> 

The current versions of Hyper-V support interrupt handling on CPU0 only.
I can make multiple buffers per channel, but because of Hyper-V implementation
It does not really make a difference.

Hank.

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