From: Andy Lutomirski <luto@kernel.org>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>, Mel Gorman <mgorman@suse.de>,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>
Subject: Re: Potential race in TLB flush batching?
Date: Wed, 12 Jul 2017 22:38:51 -0700 [thread overview]
Message-ID: <CALCETrVrP3OVgs_AjnpfOY2-aeDGRorMQ2i4jeO50kPGb-D6+g@mail.gmail.com> (raw)
In-Reply-To: <079D9048-0FFD-4A58-90EF-889259EB6ECE@gmail.com>
On Wed, Jul 12, 2017 at 4:42 PM, Nadav Amit <nadav.amit@gmail.com> wrote:
> Andy Lutomirski <luto@kernel.org> wrote:
>
>> On Wed, Jul 12, 2017 at 4:27 PM, Nadav Amit <nadav.amit@gmail.com> wrote:
>>> Actually, I think that based on Andy’s patches there is a relatively
>>> reasonable solution. For each mm we will hold both a “pending_tlb_gen”
>>> (increased under the PT-lock) and an “executed_tlb_gen”. Once
>>> flush_tlb_mm_range finishes flushing it will use cmpxchg to update the
>>> executed_tlb_gen to the pending_tlb_gen that was prior the flush (the
>>> cmpxchg will ensure the TLB gen only goes forward). Then, whenever
>>> pending_tlb_gen is different than executed_tlb_gen - a flush is needed.
>>
>> Why do we need executed_tlb_gen? We already have
>> cpu_tlbstate.ctxs[...].tlb_gen. Or is the idea that executed_tlb_gen
>> guarantees that all cpus in mm_cpumask are at least up to date to
>> executed_tlb_gen?
>
> Hm... So actually it may be enough, no? Just compare mm->context.tlb_gen
> with cpu_tlbstate.ctxs[...].tlb_gen and flush if they are different?
>
Wouldn't that still leave the races where the CPU observing the stale
TLB entry isn't the CPU that did munmap/mprotect/whatever? I think
executed_tlb_gen or similar may really be needed for your approach.
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next prev parent reply other threads:[~2017-07-13 5:39 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-11 0:52 Potential race in TLB flush batching? Nadav Amit
2017-07-11 6:41 ` Mel Gorman
2017-07-11 7:30 ` Nadav Amit
2017-07-11 9:29 ` Mel Gorman
2017-07-11 10:40 ` Nadav Amit
2017-07-11 13:20 ` Mel Gorman
2017-07-11 14:58 ` Andy Lutomirski
2017-07-11 15:53 ` Mel Gorman
2017-07-11 17:23 ` Andy Lutomirski
2017-07-11 19:18 ` Mel Gorman
2017-07-11 20:06 ` Nadav Amit
2017-07-11 21:09 ` Mel Gorman
2017-07-11 20:09 ` Mel Gorman
2017-07-11 21:52 ` Mel Gorman
2017-07-11 22:27 ` Nadav Amit
2017-07-11 22:34 ` Nadav Amit
2017-07-12 8:27 ` Mel Gorman
2017-07-12 23:27 ` Nadav Amit
2017-07-12 23:36 ` Andy Lutomirski
2017-07-12 23:42 ` Nadav Amit
2017-07-13 5:38 ` Andy Lutomirski [this message]
2017-07-13 16:05 ` Nadav Amit
2017-07-13 16:06 ` Andy Lutomirski
2017-07-13 6:07 ` Mel Gorman
2017-07-13 16:08 ` Andy Lutomirski
2017-07-13 17:07 ` Mel Gorman
2017-07-13 17:15 ` Andy Lutomirski
2017-07-13 18:23 ` Mel Gorman
2017-07-14 23:16 ` Nadav Amit
2017-07-15 15:55 ` Mel Gorman
2017-07-15 16:41 ` Andy Lutomirski
2017-07-17 7:49 ` Mel Gorman
2017-07-18 21:28 ` Nadav Amit
2017-07-19 7:41 ` Mel Gorman
2017-07-19 19:41 ` Nadav Amit
2017-07-19 19:58 ` Mel Gorman
2017-07-19 20:20 ` Nadav Amit
2017-07-19 21:47 ` Mel Gorman
2017-07-19 22:19 ` Nadav Amit
2017-07-19 22:59 ` Mel Gorman
2017-07-19 23:39 ` Nadav Amit
2017-07-20 7:43 ` Mel Gorman
2017-07-22 1:19 ` Nadav Amit
2017-07-24 9:58 ` Mel Gorman
2017-07-24 19:46 ` Nadav Amit
2017-07-25 7:37 ` Minchan Kim
2017-07-25 8:51 ` Mel Gorman
2017-07-25 9:11 ` Minchan Kim
2017-07-25 10:10 ` Mel Gorman
2017-07-26 5:43 ` Minchan Kim
2017-07-26 9:22 ` Mel Gorman
2017-07-26 19:18 ` Nadav Amit
2017-07-26 23:40 ` Minchan Kim
2017-07-27 0:09 ` Nadav Amit
2017-07-27 0:34 ` Minchan Kim
2017-07-27 0:48 ` Nadav Amit
2017-07-27 1:13 ` Nadav Amit
2017-07-27 7:04 ` Minchan Kim
2017-07-27 7:21 ` Mel Gorman
2017-07-27 16:04 ` Nadav Amit
2017-07-27 17:36 ` Mel Gorman
2017-07-26 23:44 ` Minchan Kim
2017-07-11 22:07 ` Andy Lutomirski
2017-07-11 22:33 ` Mel Gorman
2017-07-14 7:00 ` Benjamin Herrenschmidt
2017-07-14 8:31 ` Mel Gorman
2017-07-14 9:02 ` Benjamin Herrenschmidt
2017-07-14 9:27 ` Mel Gorman
2017-07-14 22:21 ` Andy Lutomirski
2017-07-11 16:22 ` Nadav Amit
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