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From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <namit@vmware.com>
Cc: linux-mm@kvack.org, nadav.amit@gmail.com,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	Minchan Kim <minchan@kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH v6 3/7] Revert "mm: numa: defer TLB flush for THP migration as long as possible"
Date: Fri, 11 Aug 2017 12:50:15 +0200	[thread overview]
Message-ID: <20170811105015.4njdpy3il76g5uuk@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170802000818.4760-4-namit@vmware.com>

On Tue, Aug 01, 2017 at 05:08:14PM -0700, Nadav Amit wrote:
> While deferring TLB flushes is a good practice, the reverted patch
> caused pending TLB flushes to be checked while the page-table lock is
> not taken. As a result, in architectures with weak memory model (PPC),
> Linux may miss a memory-barrier, miss the fact TLB flushes are pending,
> and cause (in theory) a memory corruption.
> 
> Since the alternative of using smp_mb__after_unlock_lock() was
> considered a bit open-coded, and the performance impact is expected to
> be small, the previous patch is reverted.

FWIW this Changelog sucks arse; you completely fail to explain the
broken ordering.

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  reply	other threads:[~2017-08-11 10:50 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-02  0:08 [PATCH v6 0/7] fixes of TLB batching races Nadav Amit
2017-08-02  0:08 ` [PATCH v6 1/7] mm: migrate: prevent racy access to tlb_flush_pending Nadav Amit
2017-08-02  0:08 ` [PATCH v6 2/7] mm: migrate: fix barriers around tlb_flush_pending Nadav Amit
2017-08-02  0:08 ` [PATCH v6 3/7] Revert "mm: numa: defer TLB flush for THP migration as long as possible" Nadav Amit
2017-08-11 10:50   ` Peter Zijlstra [this message]
2017-08-02  0:08 ` [PATCH v6 4/7] mm: refactoring TLB gathering API Nadav Amit
2017-08-11  9:23   ` Peter Zijlstra
2017-08-11 17:12     ` Nadav Amit
2017-08-14  0:49       ` Minchan Kim
2017-08-02  0:08 ` [PATCH v6 5/7] mm: make tlb_flush_pending global Nadav Amit
2017-08-02 14:28   ` kbuild test robot
2017-08-02 23:23     ` Minchan Kim
2017-08-02 23:27     ` Andrew Morton
2017-08-02 23:34       ` Minchan Kim
2017-08-03 16:40   ` kbuild test robot
2017-08-02  0:08 ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem Nadav Amit
2017-08-08  1:19   ` [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression kernel test robot
2017-08-08  2:28     ` Minchan Kim
2017-08-08  4:23       ` Nadav Amit
2017-08-08  5:51         ` Nadav Amit
2017-08-08  8:08           ` Minchan Kim
2017-08-08  8:16             ` Nadav Amit
2017-08-09  1:25             ` Ye Xiaolong
2017-08-09  2:59             ` Ye Xiaolong
2017-08-10  4:13               ` Minchan Kim
2017-08-10  4:14                 ` Nadav Amit
2017-08-10  4:20                   ` Minchan Kim
2017-08-11 13:30   ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem Peter Zijlstra
2017-08-13  6:14     ` Nadav Amit
2017-08-13 12:08       ` Peter Zijlstra
2017-08-14  1:26     ` Minchan Kim
2017-08-02  0:08 ` [PATCH v6 7/7] mm: fix KSM data corruption Nadav Amit
2017-08-02 23:26 ` [PATCH v6 0/7] fixes of TLB batching races Minchan Kim

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