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[23.128.96.18]) by mx.google.com with ESMTP id j93si11673492edd.458.2020.05.26.07.07.12; Tue, 26 May 2020 07:07:36 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=K5WCGqmZ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731793AbgEZOBe (ORCPT + 99 others); Tue, 26 May 2020 10:01:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:44492 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729443AbgEZOBd (ORCPT ); Tue, 26 May 2020 10:01:33 -0400 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B95B12087D; Tue, 26 May 2020 14:01:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590501692; bh=j4r2suThCDUMOafUx5RYzfeHJPTRkpk35oKAvdOKYeE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=K5WCGqmZ5rMseZLf8YqHin2gpc0dbViNYwVDJTRTpeQBCn04jLbDFdb9LZQ60RuIv YcY2BoqH2LrAhkkXK8yWKczpylPPezbYCTwT5fVpOFZcvqFU5NDGF+RDKnwFW/O6lO fx/BaU/Arjmux+MFGWjuPyfnLjv7BotY8+mzssU0= Date: Tue, 26 May 2020 15:01:27 +0100 From: Will Deacon To: Mike Rapoport Cc: Guenter Roeck , linux-kernel@vger.kernel.org, elver@google.com, tglx@linutronix.de, paulmck@kernel.org, mingo@kernel.org, peterz@infradead.org, "David S. Miller" Subject: Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables Message-ID: <20200526140126.GD27166@willie-the-truck> References: <20200511204150.27858-5-will@kernel.org> <20200517000050.GA87467@roeck-us.net> <20200517000750.GA157503@roeck-us.net> <20200518083715.GA31383@willie-the-truck> <20200520170306.GG1118872@kernel.org> <6034a1b5-d4f6-c836-142c-9b3b06db3246@roeck-us.net> <20200520195110.GH1118872@kernel.org> <20200524123256.GN1118872@kernel.org> <20200526132634.GC27166@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526132634.GC27166@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 26, 2020 at 02:26:35PM +0100, Will Deacon wrote: > On Sun, May 24, 2020 at 03:32:56PM +0300, Mike Rapoport wrote: > > On Thu, May 21, 2020 at 04:02:11PM -0700, Guenter Roeck wrote: > > > On 5/20/20 12:51 PM, Mike Rapoport wrote: > > > > On Wed, May 20, 2020 at 12:03:31PM -0700, Guenter Roeck wrote: > > > >> With above patch applied on top of Ira's patch, I get: > > > >> > > > >> BUG: spinlock recursion on CPU#0, S01syslogd/139 > > > >> lock: 0xf5448350, .magic: dead4ead, .owner: S01syslogd/139, .owner_cpu: 0 > > > >> CPU: 0 PID: 139 Comm: S01syslogd Not tainted 5.7.0-rc6-next-20200518-00002-gb178d2d56f29-dirty #1 > > > >> [f0067a64 : > > > >> do_raw_spin_lock+0xa8/0xd8 ] > > > >> [f00d5034 : > > > >> copy_page_range+0x328/0x804 ] > > > >> [f0025be4 : > > > >> dup_mm+0x334/0x434 ] > > > >> [f0027124 : > > > >> copy_process+0x1224/0x12b0 ] > > > >> [f0027344 : > > > >> _do_fork+0x54/0x30c ] > > > >> [f0027670 : > > > >> do_fork+0x5c/0x6c ] > > > >> [f000de44 : > > > >> sparc_do_fork+0x18/0x38 ] > > > >> [f000b7f4 : > > > >> do_syscall+0x34/0x40 ] > > > >> [5010cd4c : > > > >> 0x5010cd4c ] > > > >> > > > >> Looks like yet another problem. > > > > > > > > I've checked the patch above on top of the mmots which already has Ira's > > > > patches and it booted fine. I've used sparc32_defconfig to build the > > > > kernel and qemu-system-sparc with default machine and CPU. > > > > > > > > > > Try sparc32_defconfig+SMP. > > > > I see a differernt problem, but this could be related: > > > > INIT: version 2.86 booting > > rcu: INFO: rcu_sched detected stalls on CPUs/tasks: > > (detected by 0, t=5252 jiffies, g=-935, q=3) > > rcu: All QSes seen, last rcu_sched kthread activity 5252 (-68674--73926), jiffies_till_next_fqs=1, root ->qsmask 0x0 > > rcu: rcu_sched kthread starved for 5252 jiffies! g-935 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 > > rcu: Unless rcu_sched kthread gets sufficient CPU time, OOM is now expected behavior. > > rcu: RCU grace-period kthread stack dump: > > rcu_sched R running task 0 10 2 0x00000000 > > > > I'm running a bit old debian [1] with qemu-img-sparc. > > > > My bisect pointed at commit 8c8f3156dd40 ("sparc32: mm: Reduce > > allocation size for PMD and PTE tables"). The commit ID is valid for > > next-20200522. > > Can you try the diff below please? Actually, that's racy. New version below! Will --->8 diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c index c861c0f0df73..068029471aa4 100644 --- a/arch/sparc/mm/srmmu.c +++ b/arch/sparc/mm/srmmu.c @@ -363,11 +363,16 @@ pgtable_t pte_alloc_one(struct mm_struct *mm) if ((ptep = pte_alloc_one_kernel(mm)) == 0) return NULL; + page = pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - if (!pgtable_pte_page_ctor(page)) { - __free_page(page); - return NULL; + + spin_lock(&mm->page_table_lock); + if (page_ref_inc_return(page) == 2 && !pgtable_pte_page_ctor(page)) { + page_ref_dec(page); + ptep = NULL; } + spin_unlock(&mm->page_table_lock); + return ptep; } @@ -376,7 +381,12 @@ void pte_free(struct mm_struct *mm, pgtable_t ptep) struct page *page; page = pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - pgtable_pte_page_dtor(page); + + spin_lock(&mm->page_table_lock); + if (page_ref_dec_return(page) == 1) + pgtable_pte_page_dtor(page); + spin_unlock(&mm->page_table_lock); + srmmu_free_nocache(ptep, SRMMU_PTE_TABLE_SIZE); } diff --git a/mm/Kconfig b/mm/Kconfig index c1acc34c1c35..97458119cce8 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -192,6 +192,9 @@ config MEMORY_HOTREMOVE # Default to 4 for wider testing, though 8 might be more appropriate. # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. +# SPARC32 allocates multiple pte tables within a single page, and therefore +# a per-page lock leads to problems when multiple tables need to be locked +# at the same time (e.g. copy_page_range()). # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. # config SPLIT_PTLOCK_CPUS @@ -199,6 +202,7 @@ config SPLIT_PTLOCK_CPUS default "999999" if !MMU default "999999" if ARM && !CPU_CACHE_VIPT default "999999" if PARISC && !PA20 + default "999999" if SPARC32 default "4" config ARCH_ENABLE_SPLIT_PMD_PTLOCK