On Fri, Jan 23, 2015 at 02:42:17PM -0800, Tyler Baker wrote: > Hi Kirill, > > On 23 January 2015 at 12:22, Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> wrote: > > On Fri, Jan 23, 2015 at 12:37:06PM -0600, Nishanth Menon wrote: > >> On 09:39-20150123, Tyler Baker wrote: > >> > Hi, > >> > > >> > On 23 January 2015 at 09:27, Nishanth Menon <nm@xxxxxx> wrote: > >> > > On 16:05-20150120, Kirill A. Shutemov wrote: > >> > > [..] > >> > >> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > >> > >> Reported-by: Nishanth Menon <nm@xxxxxx> > >> > > Just to close on this thread: > >> > > https://github.com/nmenon/kernel-test-logs/tree/next-20150123 looks good > >> > > and back to old status. Thank you folks for all the help. > >> > > >> > I just reviewed the boot logs for next-20150123 and there still seems > >> > to be a related issue. I've been boot testing > >> > multi_v7_defconfig+CONFIG_ARM_LPAE=y kernel configurations which still > >> > seem broken. > >> > > >> > For example here are two boots with exynos5250-arndale, one with > >> > multi_v7_defconfig+CONFIG_ARM_LPAE=y [1] and the other with > >> > multi_v7_defconfig[2]. You can see the kernel configurations with > >> > CONFIG_ARM_LPAE=y show the splat: > >> > > >> > [ 14.605950] ------------[ cut here ]------------ > >> > [ 14.609163] WARNING: CPU: 1 PID: 63 at ../mm/mmap.c:2858 > >> > exit_mmap+0x1b8/0x224() > >> > [ 14.616548] Modules linked in: > >> > [ 14.619553] CPU: 1 PID: 63 Comm: init Not tainted 3.19.0-rc5-next-20150123 #1 > >> > [ 14.626713] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) > >> > [ 14.632830] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > >> > [ 14.640473] [] (show_stack) from [] (dump_stack+0x78/0x94) > >> > [ 14.647678] [] (dump_stack) from [] (warn_slowpath_common+0x74/0xb0) > >> > [ 14.655744] [] (warn_slowpath_common) from [] (warn_slowpath_null+0x1c/0x24) > >> > [ 14.664510] [] (warn_slowpath_null) from [] (exit_mmap+0x1b8/0x224) > >> > [ 14.672497] [] (exit_mmap) from [] (mmput+0x40/0xf8) > >> > [ 14.679180] [] (mmput) from [] (flush_old_exec+0x328/0x604) > >> > [ 14.686471] [] (flush_old_exec) from [] (load_elf_binary+0x26c/0x11f4) > >> > [ 14.694715] [] (load_elf_binary) from [] (search_binary_handler+0x98/0x244) > >> > [ 14.703395] [] (search_binary_handler) from [] > >> > (do_execveat_common+0x4dc/0x5bc) > >> > [ 14.712421] [] (do_execveat_common) from [] (do_execve+0x28/0x30) > >> > [ 14.720235] [] (do_execve) from [] (ret_fast_syscall+0x0/0x34) > >> > [ 14.727782] ---[ end trace 5e3ca48b454c7e0a ]--- > >> > [ 14.733758] ------------[ cut here ]------------ > >> > > >> > Has anyone else tested with CONFIG_ARM_LPAE=y that can confirm my findings? > >> Uggh... I missed since i was looking at non LPAE omap2plus_defconfig. > >> > >> Dual A15 OMAP5432 with multi_v7_defconfig + CONFIG_ARM_LPAE=y > >> https://github.com/nmenon/kernel-test-logs/blob/next-20150123/multi_lpae_defconfig/omap5-evm.txt > >> > >> Dual A15 DRA7/AM572x with same configuration as above. > >> https://raw.githubusercontent.com/nmenon/kernel-test-logs/next-20150123/multi_lpae_defconfig/dra7xx-evm.txt > >> https://github.com/nmenon/kernel-test-logs/blob/next-20150123/multi_lpae_defconfig/am57xx-evm.txt > >> > >> Single A15 DRA72 with same configuration as above: > >> https://raw.githubusercontent.com/nmenon/kernel-test-logs/next-20150123/multi_lpae_defconfig/dra72x-evm.txt > >> > >> You are right. the issue re-appears with LPAE on :( > >> Apologies on missing that. > > > > Guys, could you instrument mm_{inc,dec}_nr_pmds() with dump_stack() + > > printk() of the counter and add printk() on mmap_exit() then run a simple > > program which triggers the issue? > > For reference, here is the patch I've applied for testing, mostly > stolen from Felipe's debug patch above in this thread. > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1fbd0e8..e5b0444 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1455,11 +1455,17 @@ static inline unsigned long mm_nr_pmds(struct > mm_struct *mm) > static inline void mm_inc_nr_pmds(struct mm_struct *mm) > { > atomic_long_inc(&mm->nr_pmds); > + dump_stack(); > + printk(KERN_INFO "===> %s nr_pmds %ld\n", __func__, > + atomic_long_read(&mm->nr_pmds)); > } > > static inline void mm_dec_nr_pmds(struct mm_struct *mm) > { > atomic_long_dec(&mm->nr_pmds); > + dump_stack(); > + printk(KERN_INFO "===> %s nr_pmds %ld\n", __func__, > + atomic_long_read(&mm->nr_pmds)); > } > #endif > > diff --git a/mm/mmap.c b/mm/mmap.c > index 6a7d36d..a16471f 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2809,6 +2809,7 @@ EXPORT_SYMBOL(vm_brk); > /* Release all mmaps. */ > void exit_mmap(struct mm_struct *mm) > { > + printk(KERN_INFO "===> %s exit_mmap enter\n", __func__); > struct mmu_gather tlb; > struct vm_area_struct *vma; > unsigned long nr_accounted = 0; > > I applied this patch to the tip of linux-next, configured for > multi_v7_defconfig and set CONFIG_ARM_LPAE=y. The log for this arndale > boot can be found here [1]. For good measure, I then rebuilt the > kernel with CONFIG_ARM_LPAE=n and booted the same platform again. This > log can be found here [2]. > > Happy hunting! Okay, proof of concept patch is below. It's going to break every other architecture with FIRST_USER_ADDRESS != 0, but I think it's cleaner way to go. The problem is that we check nr_ptes/nr_pmds in exit_mmap() which happens *before* pgd_free(). And if an arch does pte/pmd allocation in pgd_alloc() and frees them in pgd_free() we see offset in counters by the time of the checks. This scenario happens for all archs with FIRST_USER_ADDRESS != 0 and we tried to work it around by offsetting expected counter value according to FIRST_USER_ADDRESS for both nr_pte and nr_pmd in exit_mmap(). But ARM with LPAE also has non-zero USER_PGTABLES_CEILING, but upper addresses occupied with huge pmd entries, so the trick with offsetting expected counter value will get really ugly: we will have to apply it nr_pmds, but not nr_ptes. The proposal is to move the check to check_mm() which happens *after* pgd_free(). We would need to adjust pgd_free() on all architectures with non-zero FIRST_USER_ADDRESS to make accouting properly there. But I think the end result would be cleaner. Andrew, any comments? diff --git a/arch/arm/mm/pgd.c b/arch/arm/mm/pgd.c index 249379535be2..c3ec18d9bbb9 100644 --- a/arch/arm/mm/pgd.c +++ b/arch/arm/mm/pgd.c @@ -130,9 +130,11 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd_base) pte = pmd_pgtable(*pmd); pmd_clear(pmd); pte_free(mm, pte); + atomic_long_dec(&mm->nr_ptes); no_pmd: pud_clear(pud); pmd_free(mm, pmd); + mm_dec_nr_pmds(mm); no_pud: pgd_clear(pgd); pud_free(mm, pud); @@ -152,6 +154,7 @@ no_pgd: pmd = pmd_offset(pud, 0); pud_clear(pud); pmd_free(mm, pmd); + mm_dec_nr_pmds(mm); pgd_clear(pgd); pud_free(mm, pud); } diff --git a/kernel/fork.c b/kernel/fork.c index c99098c52641..0a6f0a380335 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -599,6 +599,13 @@ static void check_mm(struct mm_struct *mm) { int i; + if (atomic_long_read(&mm->nr_ptes)) + pr_alert("BUG: non-zero nr_ptes on freeing mm: %ld", + atomic_long_read(&mm->nr_ptes)); + if (mm_nr_pmds(mm)) + pr_alert("BUG: non-zero nr_pmds on freeing mm: %ld", + mm_nr_pmds(mm)); + for (i = 0; i < NR_MM_COUNTERS; i++) { long x = atomic_long_read(&mm->rss_stat.count[i]); diff --git a/mm/mmap.c b/mm/mmap.c index 6a7d36d133fb..c5f44682c0d1 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2851,11 +2851,6 @@ void exit_mmap(struct mm_struct *mm) vma = remove_vma(vma); } vm_unacct_memory(nr_accounted); - - WARN_ON(atomic_long_read(&mm->nr_ptes) > - round_up(FIRST_USER_ADDRESS, PMD_SIZE) >> PMD_SHIFT); - WARN_ON(mm_nr_pmds(mm) > - round_up(FIRST_USER_ADDRESS, PUD_SIZE) >> PUD_SHIFT); } /* Insert vm structure into process list sorted by address -- Kirill A. 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