Messages in this thread | | | Date | Tue, 26 May 2020 18:21:20 +0300 | From | Mike Rapoport <> | Subject | Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables |
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On Tue, May 26, 2020 at 03:01:27PM +0100, 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!
Well, both versions worked for me with sparc32_defconfig+SMP build when I ran qemu-system-sparc with default machine (SS-5) that does not allow SMP.
I could not check with actial SMP because qemu-system-sparc -M SS-10 -smp 2 and qemu-system-sparc -M SS-20 -smp 2 fail early with an exception even in v5.7-rc7...
> 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
-- Sincerely yours, Mike.
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