Date: Tue, 15 Jun 2010 17:45:06 +0530
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
       Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       Masami Hiramatsu <mhiramat@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
       Randy Dunlap <rdunlap@xenotime.net>,
       Arnaldo Carvalho de Melo <acme@infradead.org>,
       Steven Rostedt <rostedt@goodmis.org>,
       Roland McGrath <roland@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
       Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
       Mark Wielaard <mjw@redhat.com>,
       Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Jim Keniston <jkenisto@linux.vnet.ibm.com>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, "Frank Ch. Eigler" <fche@redhat.com>,
       LKML <linux-kernel@vger.kernel.org>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v5 7/14] x86 support for Uprobes
Message-ID: <20100615121506.GM13800@linux.vnet.ibm.com>
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
References: <20100614082748.29068.21995.sendpatchset@localhost6.localdomain6>
 <20100614082913.29068.86825.sendpatchset@localhost6.localdomain6>
 <20100614175423.GG23754@infradead.org>
 <20100615062332.GE13800@linux.vnet.ibm.com>
 <20100615115155.GA4831@redhat.com>
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> > >
> > > I'm no x86 port guru, but this looks rather worriesome to me.  Why does
> > > do_notify_resume have different calling conventions on 32 vs 64-bit?
> > > And if there is a good reason that 32-bit has them disabled, why is
> > > enabling them in the middle of do_notify_resume okay?
> >
> > Thanks for bringing this up. I have no idea about why do_notify_resume()
> > gets called with interrupts disabled in 32 bit.
> 
> Perhaps just because there is no reason to explicitly enable irqs?
> 
> > I would be happy to know
> > the reason and rework based on inputs. I did query a few people about
> > this but I havent got an answer on why we they are disabled on 32 bit and
> > if its Okay to enable at this place.
> 
> I think it is OK to enable interrupts. do_notify_resume() calls do_signal()
> which enables them anyway.
> 
> But there is another question I already asked. Why the code uses
> native_irq_enable()? IIRC, you explained that local_irq_enable() doesn't
> work for unkown reason. This is strange, and imho should be explained.
> 

local_irq_enable() translates to raw_local_irq_enable().
However raw_local_irq_enable on x86 seems to depend on CONFIG_PARAVIRT.
On a machine, where CONFIG_PARAVIRT was defined, local_irq_enable
translates to something other than native_irq_enable.
It translates to PVOP_VCALLEE0(pv_irq_ops.irq_enable);

Is it okay to use local_irq_enable() and then make CONFIG_UPROBES depend
on !CONFIG_PARAVIRT?


> And I do not see a need to disable irqs again.
> 
> Oleg.
> 
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