From fbc39525ed5a591defcf66c7b32a0ab6b97b0c84 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sat, 20 Oct 2018 00:38:00 +0200 Subject: [PATCH] mm/tlb: Remove tlb_remove_table() non-concurrent condition BugLink: https://launchpad.net/bugs/1798897 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 (cherry picked from commit a6f572084fbee8b30f91465f4a085d7a90901c57) Signed-off-by: Tyler Hicks Acked-by: Kleber Sacilotto de Souza Acked-by: Stefan Bader Signed-off-by: Kleber Sacilotto de Souza --- mm/memory.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index c5928cda7748..b991e87d0bf1 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -376,15 +376,6 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table) { 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) { -- 2.39.2