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Date: Tue, 26 May 2020 10:15:38 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Mike Rapoport <rppt@...nel.org> Cc: Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org, elver@...gle.com, tglx@...utronix.de, paulmck@...nel.org, mingo@...nel.org, peterz@...radead.org, "David S. Miller" <davem@...emloft.net> Subject: Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables On 5/26/20 9:29 AM, Mike Rapoport wrote: > On Tue, May 26, 2020 at 09:18:54AM -0700, Guenter Roeck wrote: >> On 5/26/20 7:01 AM, Will Deacon wrote: >>> 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! >>> >> >> Applied on top of next-20200526, with defconfig+SMP, I still get: >> >> BUG: Bad page state in process swapper/0 pfn:0069f >> >> many times. Did I have to revert something else ? Sorry, I lost track. > > The bad page messages are fixed by [1], but this is not in mmotm or > linux-next. This is not related to SMP hangs. > > [1] https://lore.kernel.org/lkml/20200524165358.27188-1-rppt@kernel.org/ > With that applied, all boot tests pass for me (including tests with "-smp 2" on SS-10). Guenter >> Note that "-smp 2" on SS-10 works for me (with the same page state >> messages). >> >> Guenter >> >> >>> 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 >>> >> >
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