linux-kernel - [tip: x86/mm] mm: Remove pointless barrier() after pmdp_get

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Date:   Wed, 02 Nov 2022 09:12:32 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/mm] mm: Remove pointless barrier() after pmdp_get_lockless()

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     0aa82c4e78ca59a2246a28112adbee7d0a692f27
Gitweb:        https://git.kernel.org/tip/0aa82c4e78ca59a2246a28112adbee7d0a692f27
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 21 Oct 2022 13:47:29 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 01 Nov 2022 13:44:05 +01:00

mm: Remove pointless barrier() after pmdp_get_lockless()

pmdp_get_lockless() should itself imply any ordering required.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20221022114425.298833095%40infradead.org
---
 mm/hmm.c    | 1 -
 mm/vmscan.c | 3 ---
 2 files changed, 4 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 39cf50d..601a99c 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -362,7 +362,6 @@ again:
 		 * values.
 		 */
 		pmd = pmdp_get_lockless(pmdp);
-		barrier();
 		if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
 			goto again;
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 88ef873..4936a88 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4041,9 +4041,6 @@ restart:
 	for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
 		pmd_t val = pmdp_get_lockless(pmd + i);
 
-		/* for pmdp_get_lockless() */
-		barrier();
-
 		next = pmd_addr_end(addr, end);
 
 		if (!pmd_present(val) || is_huge_zero_pmd(val)) {