From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:56894 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729993AbeIHC0W (ORCPT ); Fri, 7 Sep 2018 22:26:22 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , "Peter Zijlstra (Intel)" , Rik van Riel , Nicholas Piggin , David Miller , Martin Schwidefsky , Michael Ellerman , stable@kernel.org, Linus Torvalds Subject: [PATCH 3.18 17/29] mm/tlb: Remove tlb_remove_table() non-concurrent condition Date: Fri, 7 Sep 2018 23:10:38 +0200 Message-Id: <20180907210910.759447458@linuxfoundation.org> In-Reply-To: <20180907210909.523240901@linuxfoundation.org> References: <20180907210909.523240901@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit a6f572084fbee8b30f91465f4a085d7a90901c57 upstream. Will noted that only checking mm_users is incorrect; we should also check mm_count in order to cover CPUs that have a lazy reference to this mm (and could do speculative TLB operations). If removing this turns out to be a performance issue, we can re-instate a more complete check, but in tlb_table_flush() eliding the call_rcu_sched(). Fixes: 267239116987 ("mm, powerpc: move the RCU page-table freeing into generic code") Reported-by: Will Deacon Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rik van Riel Acked-by: Will Deacon Cc: Nicholas Piggin Cc: David Miller Cc: Martin Schwidefsky Cc: Michael Ellerman Cc: stable@kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 9 --------- 1 file changed, 9 deletions(-) --- a/mm/memory.c +++ b/mm/memory.c @@ -359,15 +359,6 @@ void tlb_remove_table(struct mmu_gather { struct mmu_table_batch **batch = &tlb->batch; - /* - * When there's less then two users of this mm there cannot be a - * concurrent page-table walk. - */ - if (atomic_read(&tlb->mm->mm_users) < 2) { - __tlb_remove_table(table); - return; - } - if (*batch == NULL) { *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN); if (*batch == NULL) {