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Date:   Sat, 21 Jul 2018 19:39:44 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Davidlohr Bueso <dave@stgolabs.net>
Cc:     Andrew Morton <akpm@linux-foundation.org>, jbaron@akamai.com,
        viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next 0/2] fs/epoll: loosen irq safety when possible
Message-ID: <20180721173944.GV2494@hirez.programming.kicks-ass.net>
References: <20180720172956.2883-1-dave@stgolabs.net>
 <20180720124212.7260d76d83e2b8e5e3349ea5@linux-foundation.org>
 <20180720200559.27nc7j2rrxpy5p3n@linux-r8p5>
 <20180720134429.1ba61018934b084bb2e17bdb@linux-foundation.org>
 <20180721172120.kbdu4euc2wn4xzgf@linux-r8p5>
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On Sat, Jul 21, 2018 at 10:21:20AM -0700, Davidlohr Bueso wrote:
> On Fri, 20 Jul 2018, Andrew Morton wrote:
> 
> > We could open-code it locally.  Add a couple of
> > WARN_ON_ONCE(irqs_disabled())?  That might need re-benchmarking with
> > Xen but surely just reading the thing isn't too expensive?
> 
> We could also pass on the responsibility to lockdep and just use
> lockdep_assert_irqs_disabled(). But I guess that would be less effective
> than to just open code it in epoll without lockdep -- note that over 80
> places in the kernel do this.

The lockdep thing is relatively recent. I think someone proposed to go
replace a bunch of the open-coded ones at some point.