From: Peter Zijlstra <peterz@infradead.org>
To: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, Davidlohr Bueso <dave@stgolabs.net>,
akpm@linux-foundation.org, Jan Kara <jack@suse.cz>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
haren@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com,
khandual@linux.vnet.ibm.com, Paul.McKenney@us.ibm.com,
linux-kernel@vger.kernel.org
Subject: Re: [RFC 2/4] Deactivate mmap_sem assert
Date: Wed, 19 Apr 2017 15:54:23 +0200 [thread overview]
Message-ID: <20170419135423.r5zykftem6hrusny@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <e6397c6c-6718-a0f3-0d72-7ad85760fdea@linux.vnet.ibm.com>
On Wed, Apr 19, 2017 at 03:45:50PM +0200, Laurent Dufour wrote:
> On 19/04/2017 14:30, Peter Zijlstra wrote:
> > On Wed, Apr 19, 2017 at 02:18:25PM +0200, Laurent Dufour wrote:
> >> When mmap_sem will be moved to a range lock, some assertion done in
> >> the code are no more valid, like the one ensuring mmap_sem is held.
> >>
> >
> > Why are they no longer valid?
>
> I didn't explain that very well..
>
> When using a range lock we can't check that the lock is simply held, but
> if the range we are interesting on is locked or not.
I don't think it matters.. That is, in general you cannot assume
anything about the ranges, therefore, for deadlock analysis you have to
assume each range is the full range.
Once you're there, and assume that each range is the full range, this
test is once again trivial.
The fact that not all ranges are the full range, is merely a performance
consideration, but should not be a correctness issue.
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next prev parent reply other threads:[~2017-04-19 13:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 12:18 [RFC 0/4] Replace mmap_sem by a range lock Laurent Dufour
2017-04-19 12:18 ` [RFC 1/4] Add additional range parameter to GUP() and handle_page_fault() Laurent Dufour
2017-04-19 12:18 ` [RFC 2/4] Deactivate mmap_sem assert Laurent Dufour
2017-04-19 12:30 ` Peter Zijlstra
2017-04-19 13:45 ` Laurent Dufour
2017-04-19 13:54 ` Peter Zijlstra [this message]
2017-04-19 12:18 ` [RFC 3/4] Remove nest locking operation with mmap_sem Laurent Dufour
2017-04-19 12:18 ` [RFC 4/4] Change mmap_sem to range lock Laurent Dufour
2017-04-20 13:33 ` [RFC 0/4] Replace mmap_sem by a " Matthew Wilcox
2017-04-20 14:39 ` Laurent Dufour
2017-04-20 14:28 ` [RFC 4/4] Change mmap_sem to " Laurent Dufour
2017-04-20 14:37 ` Peter Zijlstra
2017-04-20 14:42 ` Laurent Dufour
2017-04-20 23:36 ` Andi Kleen
2017-04-24 15:47 ` Laurent Dufour
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