Messages in this thread |  | | Date | Mon, 9 Dec 2019 17:26:49 +0530 | From | Bharata B Rao <> | Subject | Re: [PATCH 00/16] The new slab memory controller |
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On Mon, Dec 09, 2019 at 02:47:52PM +0530, Bharata B Rao wrote: > Hi, > > I see the below crash during early boot when I try this patchset on > PowerPC host. I am on new_slab.rfc.v5.3 branch. > > BUG: Unable to handle kernel data access at 0x81030236d1814578 > Faulting instruction address: 0xc0000000002cc314 > Oops: Kernel access of bad area, sig: 11 [#1] > LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV > Modules linked in: ip_tables x_tables autofs4 sr_mod cdrom usbhid bnx2x crct10dif_vpmsum crct10dif_common mdio libcrc32c crc32c_vpmsum > CPU: 31 PID: 1752 Comm: keyboard-setup. Not tainted 5.3.0-g9bd85fd72a0c #155 > NIP: c0000000002cc314 LR: c0000000002cc2e8 CTR: 0000000000000000 > REGS: c000001e40f378b0 TRAP: 0380 Not tainted (5.3.0-g9bd85fd72a0c) > MSR: 900000010280b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE,TM[E]> CR: 44022224 XER: 00000000 > CFAR: c0000000002c6ad4 IRQMASK: 1 > GPR00: c0000000000b8a40 c000001e40f37b40 c000000000ed9600 0000000000000000 > GPR04: 0000000000000023 0000000000000010 c000001e40f37b24 c000001e3cba3400 > GPR08: 0000000000000020 81030218815f4578 0000001e50220000 0000000000000030 > GPR12: 0000000000002200 c000001fff774d80 0000000000000000 00000001072600d8 > GPR16: 0000000000000000 c0000000000bbaac 0000000000000000 0000000000000000 > GPR20: c000001e40f37c48 0000000000000001 0000000000000000 c000001e3cba3400 > GPR24: c000001e40f37dd8 0000000000000000 c000000000fa0d58 0000000000000000 > GPR28: c000001e3a080080 c000001e32da0100 0000000000000118 0000000000000010 > NIP [c0000000002cc314] __mod_memcg_state+0x58/0xd0 > LR [c0000000002cc2e8] __mod_memcg_state+0x2c/0xd0 > Call Trace: > [c000001e40f37b90] [c0000000000b8a40] account_kernel_stack+0xa4/0xe4 > [c000001e40f37bd0] [c0000000000ba4a4] copy_process+0x2b4/0x16f0 > [c000001e40f37cf0] [c0000000000bbaac] _do_fork+0x9c/0x3e4 > [c000001e40f37db0] [c0000000000bc030] sys_clone+0x74/0xa8 > [c000001e40f37e20] [c00000000000bb34] ppc_clone+0x8/0xc > Instruction dump: > 4bffa7e9 2fa30000 409e007c 395efffb 3d000020 2b8a0001 409d0008 39000020 > e93d0718 e94d0028 7bde1f24 7d29f214 <7ca9502a> 7fff2a14 7fe9fe76 7d27fa78 > > Looks like page->mem_cgroup_vec is allocated but not yet initialized > with memcg pointers when we try to access them. > > I did get past the crash by initializing the pointers like this > in account_kernel_stack(),
The above is not an accurate description of the hack I showed below. Essentially I am making sure that I get to the memcg corresponding to task_struct_cachep object in the page.
But that still doesn't explain why we don't hit this problem on x86.
> but I am pretty sure that this is not the > place to do this: > > diff --git a/kernel/fork.c b/kernel/fork.c > index 541fd805fb88..be21419feae2 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -380,13 +380,26 @@ static void account_kernel_stack(struct task_struct *tsk, int account) > * All stack pages are in the same zone and belong to the > * same memcg. > */ > - struct page *first_page = virt_to_page(stack); > + struct page *first_page = virt_to_head_page((stack)); > + unsigned long off; > + struct mem_cgroup_ptr *memcg_ptr; > + struct mem_cgroup *memcg; > > mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, > THREAD_SIZE / 1024 * account); > > - mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB, > + if (!first_page->mem_cgroup_vec) > + return; > + off = obj_to_index(task_struct_cachep, first_page, stack); > + memcg_ptr = first_page->mem_cgroup_vec[off]; > + if (!memcg_ptr) > + return; > + rcu_read_lock(); > + memcg = memcg_ptr->memcg; > + if (memcg) > + __mod_memcg_state(memcg, MEMCG_KERNEL_STACK_KB, > account * (THREAD_SIZE / 1024)); > + rcu_read_unlock(); > } > } > > Regards, > Bharata.
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