Messages in this thread | | | Subject | Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and PTE tables | From | Guenter Roeck <> | Date | Wed, 20 May 2020 12:03:31 -0700 |
| |
On 5/20/20 10:03 AM, Mike Rapoport wrote: > On Mon, May 18, 2020 at 09:37:15AM +0100, Will Deacon wrote: >> On Sat, May 16, 2020 at 05:07:50PM -0700, Guenter Roeck wrote: >>> On Sat, May 16, 2020 at 05:00:50PM -0700, Guenter Roeck wrote: >>>> On Mon, May 11, 2020 at 09:41:36PM +0100, Will Deacon wrote: >>>>> Now that the page table allocator can free page table allocations >>>>> smaller than PAGE_SIZE, reduce the size of the PMD and PTE allocations >>>>> to avoid needlessly wasting memory. >>>>> >>>>> Cc: "David S. Miller" <davem@davemloft.net> >>>>> Cc: Peter Zijlstra <peterz@infradead.org> >>>>> Signed-off-by: Will Deacon <will@kernel.org> >>>> >>>> Something in the sparc32 patches in linux-next causes all my sparc32 emulations >>>> to crash. bisect points to this patch, but reverting it doesn't help, and neither >>>> does reverting the rest of the series. >>>> >>> Actually, turns out I see the same pattern (lots of scheduling while atomic >>> followed by 'killing interrupt handler' in cryptomgr_test) with several >>> powerpc boot tests. I am currently bisecting those crashes. I'll report >>> the results here as well as soon as I have it. >> >> FWIW, I retested my sparc32 patches with PREEMPT=y and I don't see any >> issues. However, linux-next is a different story, where I don't get very far >> at all: >> >> BUG: Bad page state in process swapper pfn:005b4 > > This is caused by c03584e30534 ("mm: memmap_init: iterate over memblock > regions rather that check each PFN"). The commit sha is valid for > v5.7-rc6-mmots-2020-05-19-21-52, so it will change in a day or so :) > > As it seems, sparc32 never registered the memory occupied by the kernel > image with memblock_add() and it only reserves this memory with > meblock_reserve(). > > I don't know what would happen on real HW, but with > > qemu-system-sparc -kernel /path/to/kernel > > the memory occupied by the kernel is reserved in openbios and removed > from mem.available. The prom setup code in the kernel used mem.available > to set up the memory banks and essentially there is a hole for the > memory occupied by the kernel. > > Later in bootmem_init() this memory is memblock_reserve()d. > > Before the problematic commit, memmap initialization would call > __init_single_page() for the pages in that hole, the > free_low_memory_core_early() would mark them as resrved and everything > would be Ok. > > After the change in memmap initialization, the hole is skipped and the > page structs for it are not inited. And when they are passed from > memblock to page allocator as reserved it gets confused. > > Simply registering the memory occupied by the kernel with memblock_add() > resolves this issue, at least for qemu-system-arm and I cannot see how > it can harm any other setup. > > If all that makes sense I'll send a proper patch :) > > diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c > index 906eda1158b4..3cb3dffcbcdc 100644 > --- a/arch/sparc/mm/init_32.c > +++ b/arch/sparc/mm/init_32.c > @@ -193,6 +193,7 @@ unsigned long __init bootmem_init(unsigned long *pages_avail) > /* Reserve the kernel text/data/bss. */ > size = (start_pfn << PAGE_SHIFT) - phys_base; > memblock_reserve(phys_base, size); > + memblock_add(phys_base, size); > > size = memblock_phys_mem_size() - memblock_reserved_size(); > *pages_avail = (size >> PAGE_SHIFT) - high_pages; > >> Will >
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 can not revert c03584e30534 because it results in a compile failure.
Guenter
| |