From: Andrew Morton <akpm@linux-foundation.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linux-mm@kvack.org, Suresh Siddha <suresh.b.siddha@intel.com>,
"David S. Miller" <davem@davemloft.net>,
Hugh Dickins <hughd@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Suresh Siddha <sbsiddha@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC PATCH] mm: generalise COW SMC TLB flushing race comment
Date: Fri, 18 Dec 2020 10:58:20 -0800 [thread overview]
Message-ID: <20201218105820.1806d97ae37db3b93cb8192d@linux-foundation.org> (raw)
In-Reply-To: <20201215121119.351650-1-npiggin@gmail.com>
On Tue, 15 Dec 2020 22:11:19 +1000 Nicholas Piggin <npiggin@gmail.com> wrote:
> I'm not sure if I'm completely missing something here, but AFAIKS the
> reference to the mysterious "COW SMC race" confuses the issue. The original
> changelog and mailing list thread didn't help me either.
>
> This SMC race is where the problem was detected, but isn't the general
> problem bigger and more obvious: that the new PTE could be picked
> up at any time by any TLB while entries for the old PTE exist in other
> TLBs before the TLB flush takes effect?
>
> The case where the iTLB and dTLB of a CPU are pointing at different
> pages is an interesting one but follows from the general problem.
>
> The other (minor) thing with the comment I think it makes it a bit
> clearer to say what the old code was doing (i.e., it avoids the race
> as opposed to what?).
Could we please have a signed-off-by for this?
prev parent reply other threads:[~2020-12-18 18:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-15 12:11 [RFC PATCH] mm: generalise COW SMC TLB flushing race comment Nicholas Piggin
2020-12-15 13:36 ` Matthew Wilcox
2020-12-18 18:58 ` Andrew Morton [this message]
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