From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from Galois.linutronix.de (linutronix.de [IPv6:2001:470:1f0b:db:abcd:42:0:1]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 260331A01EC for ; Tue, 8 Mar 2016 01:37:10 +1100 (AEDT) Date: Mon, 7 Mar 2016 14:55:06 +0100 From: Sebastian Andrzej Siewior To: linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt Cc: Paul Mackerras , Michael Ellerman , "Aneesh Kumar K.V" , Christoph Lameter , Tiejun Chen , Scott Wood Subject: [PATCH] powerpc: mm: fixup preempt undefflow with huge pages Message-ID: <20160307135506.GA12595@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , hugepd_free() used __get_cpu_var() once. Nothing ensured that the code accessing the variable did not migrate from one CPU to another and soon this was noticed by Tiejun Chen in 94b09d755462 ("powerpc/hugetlb: Replace __get_cpu_var with get_cpu_var"). So we had it fixed. Christoph Lameter was doing his __get_cpu_var() replaces and forgot PowerPC. Then he noticed this and sent his fixed up batch again which got applied as 69111bac42f5 ("powerpc: Replace __get_cpu_var uses"). The careful reader will noticed one little detail: get_cpu_var() got replaced with this_cpu_ptr(). So now we have a put_cpu_var() which does a preempt_enable() and nothing that does preempt_disable() so we underflow the preempt counter. Cc: Benjamin Herrenschmidt Cc: Christoph Lameter Cc: Michael Ellerman Cc: Tiejun Chen Cc: Signed-off-by: Sebastian Andrzej Siewior --- arch/powerpc/mm/hugetlbpage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c index 744e24bcb85c..9e8919b39640 100644 --- a/arch/powerpc/mm/hugetlbpage.c +++ b/arch/powerpc/mm/hugetlbpage.c @@ -414,7 +414,7 @@ static void hugepd_free(struct mmu_gather *tlb, void *hugepte) { struct hugepd_freelist **batchp; - batchp = this_cpu_ptr(&hugepd_freelist_cur); + batchp = get_cpu_ptr(&hugepd_freelist_cur); if (atomic_read(&tlb->mm->mm_users) < 2 || cpumask_equal(mm_cpumask(tlb->mm), -- 2.7.0