From: Minchan Kim <minchan@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
"H. Peter Anvin" <hpa@zytor.com>,
Linux-Next Mailing List <linux-next@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nadav Amit <namit@vmware.com>,
Linus <torvalds@linux-foundation.org>
Subject: Re: linux-next: manual merge of the akpm-current tree with the tip tree
Date: Mon, 14 Aug 2017 12:09:14 +0900 [thread overview]
Message-ID: <20170814030914.GC25427@bbox> (raw)
In-Reply-To: <20170811140450.irhxa2bhdpmmhhpv@hirez.programming.kicks-ass.net>
Hi Peter,
On Fri, Aug 11, 2017 at 04:04:50PM +0200, Peter Zijlstra wrote:
>
> Ok, so I have the below to still go on-top.
>
> Ideally someone would clarify the situation around
> mm_tlb_flush_nested(), because ideally we'd remove the
> smp_mb__after_atomic() and go back to relying on PTL alone.
>
> This also removes the pointless smp_mb__before_atomic()
I'm not an expert of barrier stuff but IIUC, mm_tlb_flush_nested's
side full memory barrier can go with removing smp_mb__after_atomic
in inc_tlb_flush_pending side?
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 490af494c2da..5ad0e66df363 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -544,7 +544,12 @@ static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
*/
static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
{
- return atomic_read(&mm->tlb_flush_pending) > 1;
+ /*
+ * atomic_dec_and_test's full memory barrier guarantees
+ * to see uptodate tlb_flush_pending count in other CPU
+ * without relying on page table lock.
+ */
+ return !atomic_dec_and_test(&mm->tlb_flush_pending);
}
static inline void init_tlb_flush_pending(struct mm_struct *mm)
diff --git a/mm/memory.c b/mm/memory.c
index f571b0eb9816..e90b57bc65fb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -407,6 +407,10 @@ void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
unsigned long start, unsigned long end)
{
arch_tlb_gather_mmu(tlb, mm, start, end);
+ /*
+ * couterpart is mm_tlb_flush_nested in tlb_finish_mmu
+ * which decreases pending count.
+ */
inc_tlb_flush_pending(tlb->mm);
}
@@ -446,9 +450,7 @@ void tlb_finish_mmu(struct mmu_gather *tlb,
*
*/
bool force = mm_tlb_flush_nested(tlb->mm);
-
arch_tlb_finish_mmu(tlb, start, end, force);
- dec_tlb_flush_pending(tlb->mm);
}
/*
next prev parent reply other threads:[~2017-08-14 3:09 UTC|newest]
Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-11 7:53 linux-next: manual merge of the akpm-current tree with the tip tree Stephen Rothwell
2017-08-11 9:34 ` Peter Zijlstra
2017-08-11 10:48 ` Peter Zijlstra
2017-08-11 11:45 ` Stephen Rothwell
2017-08-11 11:56 ` Ingo Molnar
2017-08-11 12:17 ` Peter Zijlstra
2017-08-11 12:44 ` Ingo Molnar
2017-08-11 13:49 ` Stephen Rothwell
2017-08-11 14:04 ` Peter Zijlstra
2017-08-13 6:06 ` Nadav Amit
2017-08-13 12:50 ` Peter Zijlstra
2017-08-14 3:16 ` Minchan Kim
2017-08-14 5:07 ` Nadav Amit
2017-08-14 5:23 ` Minchan Kim
2017-08-14 8:38 ` Minchan Kim
2017-08-14 19:57 ` Peter Zijlstra
2017-08-16 4:14 ` Minchan Kim
2017-08-14 19:38 ` Peter Zijlstra
2017-08-15 7:51 ` Nadav Amit
2017-08-14 3:09 ` Minchan Kim [this message]
2017-08-14 18:54 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2022-02-16 5:38 Stephen Rothwell
2021-10-07 6:27 Stephen Rothwell
2021-03-22 6:12 Stephen Rothwell
2020-12-11 8:56 Stephen Rothwell
2020-12-11 12:47 ` Jason Gunthorpe
2020-11-27 7:48 Stephen Rothwell
2020-11-27 7:39 Stephen Rothwell
2020-11-27 11:54 ` Andy Shevchenko
2020-11-30 9:27 ` Thomas Gleixner
2020-11-23 8:05 Stephen Rothwell
2020-11-09 6:00 Stephen Rothwell
2020-10-13 6:59 Stephen Rothwell
2020-07-17 10:19 Stephen Rothwell
2020-05-29 11:05 Stephen Rothwell
2020-05-29 10:18 Stephen Rothwell
2020-05-29 10:05 Stephen Rothwell
2020-05-29 9:58 Stephen Rothwell
2020-05-25 11:04 Stephen Rothwell
2020-05-26 4:41 ` Singh, Balbir
2020-06-03 4:43 ` Stephen Rothwell
2020-05-19 16:18 Stephen Rothwell
2020-03-25 7:48 Stephen Rothwell
2020-03-19 6:42 Stephen Rothwell
2020-01-20 6:37 Stephen Rothwell
2020-01-20 6:30 Stephen Rothwell
2019-10-31 5:43 Stephen Rothwell
2019-06-24 10:24 Stephen Rothwell
2019-05-01 11:10 Stephen Rothwell
2019-01-31 4:31 Stephen Rothwell
2018-08-20 4:32 Stephen Rothwell
2018-08-20 19:52 ` Andrew Morton
2018-03-23 5:59 Stephen Rothwell
2017-12-18 5:04 Stephen Rothwell
2017-11-10 4:33 Stephen Rothwell
2017-11-02 7:19 Stephen Rothwell
2017-08-22 6:57 Stephen Rothwell
2017-08-23 6:39 ` Vlastimil Babka
2017-04-12 6:46 Stephen Rothwell
2017-04-12 20:53 ` Vlastimil Babka
2017-04-20 2:17 ` NeilBrown
2017-03-24 5:25 Stephen Rothwell
2017-02-17 4:40 Stephen Rothwell
2016-11-14 6:08 Stephen Rothwell
2016-07-29 4:14 Stephen Rothwell
2016-06-15 5:23 Stephen Rothwell
2016-06-18 19:39 ` Manfred Spraul
2016-04-29 6:12 Stephen Rothwell
2016-04-29 6:26 ` Ingo Molnar
2016-03-02 5:40 Stephen Rothwell
2016-02-26 5:07 Stephen Rothwell
2016-02-26 21:35 ` Andrew Morton
2016-02-19 4:09 Stephen Rothwell
2016-02-19 15:26 ` Ard Biesheuvel
2015-12-07 8:06 Stephen Rothwell
2015-10-02 4:21 Stephen Rothwell
2015-07-28 6:00 Stephen Rothwell
2015-07-29 17:12 ` Andrea Arcangeli
2015-07-29 17:47 ` Andy Lutomirski
2015-07-29 18:46 ` Thomas Gleixner
2015-07-30 15:38 ` Andrea Arcangeli
2015-07-29 23:06 ` Stephen Rothwell
2015-07-29 23:07 ` Thomas Gleixner
2015-09-07 23:35 ` Stephen Rothwell
2015-09-08 18:11 ` Linus Torvalds
2015-09-08 22:56 ` Stephen Rothwell
2015-09-08 23:03 ` Linus Torvalds
2015-09-08 23:21 ` Andrew Morton
2015-09-16 6:58 ` Geert Uytterhoeven
2015-06-04 12:07 Stephen Rothwell
2015-04-08 8:28 Stephen Rothwell
2015-04-08 8:25 Stephen Rothwell
2014-03-17 9:31 Stephen Rothwell
2014-03-17 9:36 ` Peter Zijlstra
2014-03-19 23:27 ` Andrew Morton
2014-01-14 4:53 Stephen Rothwell
2014-01-14 5:04 ` Davidlohr Bueso
2014-01-14 12:51 ` Peter Zijlstra
2014-01-14 13:17 ` Geert Uytterhoeven
2014-01-14 13:33 ` Peter Zijlstra
2014-01-14 16:19 ` H. Peter Anvin
2014-01-14 15:15 ` H. Peter Anvin
2014-01-14 15:20 ` Geert Uytterhoeven
2014-01-14 15:41 ` Peter Zijlstra
2014-01-14 15:48 ` H. Peter Anvin
2014-01-07 6:00 Stephen Rothwell
2014-01-07 6:34 ` Tang Chen
2013-11-08 7:48 Stephen Rothwell
2013-11-08 18:58 ` Josh Triplett
2013-11-08 23:20 ` Stephen Rothwell
2013-11-09 0:19 ` Josh Triplett
2013-10-30 6:40 Stephen Rothwell
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