From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
To: Jan Kara <jack@suse.cz>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
mingo@kernel.org, peterz@infradead.org,
akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
mhocko@suse.com, mgorman@techsingularity.net,
linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH 2/6] locking: Introduce range reader/writer lock
Date: Thu, 13 Apr 2017 10:58:04 +0200 [thread overview]
Message-ID: <19907583-178e-94a2-4297-52583cf285fb@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170413083817.GC21025@quack2.suse.cz>
On 13/04/2017 10:38, Jan Kara wrote:
> On Thu 13-04-17 10:07:48, Laurent Dufour wrote:
>> On 06/04/2017 18:50, Davidlohr Bueso wrote:
>>> On Thu, 06 Apr 2017, Laurent Dufour wrote:
>>>
>>>> How is 'seqnum' wrapping handled here ?
>>>> I'd rather see something like time_before() here, isn't it ?
>>>
>>> Its a 64bit counter, no overflows.
>>
>> I should have miss something, what prevents this 64bit counter to not
>> overflow ?
>> At some point of time, this counter could reach ~0UL and then 0UL, which
>> is breaking this check.
>
> Count for yourself how long would it take for the counter to overflow if we
> incremented it say every nanosecond?
I do agree that this will take time, but systems become larger and
having 200 threads hitting a lock like the mmap_sem every nanoseconds,
it will increment faster (still need about 3 years)... if there are 1000
threads, less than 1 year to overflow this counter...
This is not for today, I agree.
next prev parent reply other threads:[~2017-04-13 8:58 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-06 8:46 [PATCH v2 -tip 0/6] " Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 1/6] interval-tree: Build unconditionally Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 2/6] locking: Introduce range reader/writer lock Davidlohr Bueso
2017-04-06 9:01 ` Laurent Dufour
2017-04-06 16:50 ` Davidlohr Bueso
2017-04-13 8:07 ` Laurent Dufour
2017-04-13 8:38 ` Jan Kara
2017-04-13 8:58 ` Laurent Dufour [this message]
2017-04-06 10:24 ` Peter Zijlstra
2017-04-18 13:57 ` Laurent Dufour
2017-04-20 16:01 ` Davidlohr Bueso
2017-04-21 7:00 ` Laurent Dufour
2017-04-06 8:46 ` [PATCH 3/6] locking/locktorture: Fix rwsem reader_delay Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 4/6] locking/locktorture: Fix num reader/writer corner cases Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 5/6] locking/locktorture: Support range rwlocks Davidlohr Bueso
2017-04-06 8:46 ` [PATCH 6/6] staging/lustre: Use generic range rwlock Davidlohr Bueso
2017-04-07 10:08 ` Dilger, Andreas
2017-04-19 12:37 ` [PATCH v2 -tip 0/6] locking: Introduce range reader/writer lock Peter Zijlstra
2017-04-20 17:13 ` Davidlohr Bueso
2017-04-20 17:53 ` Peter Zijlstra
2017-04-20 18:36 ` Davidlohr Bueso
2017-04-20 19:10 ` Peter Zijlstra
2017-05-15 9:19 ` Davidlohr Bueso
2017-05-15 9:07 [PATCH v3 " Davidlohr Bueso
2017-05-15 9:07 ` [PATCH 2/6] " Davidlohr Bueso
2017-05-15 13:02 ` Peter Zijlstra
2017-05-16 22:19 ` Davidlohr Bueso
2017-05-15 13:44 ` Peter Zijlstra
2017-05-16 21:17 ` Davidlohr Bueso
2017-05-15 13:59 ` Peter Zijlstra
2017-05-23 15:12 ` Laurent Dufour
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