[Cc Andrew - the patch is http://lkml.kernel.org/r/1593641660-13254-2-git-send-email-bhsharma@xxxxxxxxxx] On Thu 02-07-20 08:00:27, Michal Hocko wrote: > On Thu 02-07-20 03:44:19, Bhupesh Sharma wrote: > > Prabhakar reported an OOPS inside mem_cgroup_get_nr_swap_pages() > > function in a corner case seen on some arm64 boards when kdump kernel > > runs with "cgroup_disable=memory" passed to the kdump kernel via > > bootargs. > > > > The root-cause behind the same is that currently mem_cgroup_swap_init() > > function is implemented as a subsys_initcall() call instead of a > > core_initcall(), this means 'cgroup_memory_noswap' still > > remains set to the default value (false) even when memcg is disabled via > > "cgroup_disable=memory" boot parameter. > > > > This may result in premature OOPS inside mem_cgroup_get_nr_swap_pages() > > function in corner cases: > > > > [ 0.265617] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000188 > > [ 0.274495] Mem abort info: > > [ 0.277311] ESR = 0x96000006 > > [ 0.280389] EC = 0x25: DABT (current EL), IL = 32 bits > > [ 0.285751] SET = 0, FnV = 0 > > [ 0.288830] EA = 0, S1PTW = 0 > > [ 0.291995] Data abort info: > > [ 0.294897] ISV = 0, ISS = 0x00000006 > > [ 0.298765] CM = 0, WnR = 0 > > [ 0.301757] [0000000000000188] user address but active_mm is swapper > > [ 0.308174] Internal error: Oops: 96000006 [#1] SMP > > [ 0.313097] Modules linked in: > > <..snip..> > > [ 0.331384] pstate: 00400009 (nzcv daif +PAN -UAO BTYPE=--) > > [ 0.337014] pc : mem_cgroup_get_nr_swap_pages+0x9c/0xf4 > > [ 0.342289] lr : mem_cgroup_get_nr_swap_pages+0x68/0xf4 > > [ 0.347564] sp : fffffe0012b6f800 > > [ 0.350905] x29: fffffe0012b6f800 x28: fffffe00116b3000 > > [ 0.356268] x27: fffffe0012b6fb00 x26: 0000000000000020 > > [ 0.361631] x25: 0000000000000000 x24: fffffc00723ffe28 > > [ 0.366994] x23: fffffe0010d5b468 x22: fffffe00116bfa00 > > [ 0.372357] x21: fffffe0010aabda8 x20: 0000000000000000 > > [ 0.377720] x19: 0000000000000000 x18: 0000000000000010 > > [ 0.383082] x17: 0000000043e612f2 x16: 00000000a9863ed7 > > [ 0.388445] x15: ffffffffffffffff x14: 202c303d70617773 > > [ 0.393808] x13: 6f6e5f79726f6d65 x12: 6d5f70756f726763 > > [ 0.399170] x11: 2073656761705f70 x10: 6177735f726e5f74 > > [ 0.404533] x9 : fffffe00100e9580 x8 : fffffe0010628160 > > [ 0.409895] x7 : 00000000000000a8 x6 : fffffe00118f5e5e > > [ 0.415258] x5 : 0000000000000001 x4 : 0000000000000000 > > [ 0.420621] x3 : 0000000000000000 x2 : 0000000000000000 > > [ 0.425983] x1 : 0000000000000000 x0 : fffffc0060079000 > > [ 0.431346] Call trace: > > [ 0.433809] mem_cgroup_get_nr_swap_pages+0x9c/0xf4 > > [ 0.438735] shrink_lruvec+0x404/0x4f8 > > [ 0.442516] shrink_node+0x1a8/0x688 > > [ 0.446121] do_try_to_free_pages+0xe8/0x448 > > [ 0.450429] try_to_free_pages+0x110/0x230 > > [ 0.454563] __alloc_pages_slowpath.constprop.106+0x2b8/0xb48 > > [ 0.460366] __alloc_pages_nodemask+0x2ac/0x2f8 > > [ 0.464938] alloc_page_interleave+0x20/0x90 > > [ 0.469246] alloc_pages_current+0xdc/0xf8 > > [ 0.473379] atomic_pool_expand+0x60/0x210 > > [ 0.477514] __dma_atomic_pool_init+0x50/0xa4 > > [ 0.481910] dma_atomic_pool_init+0xac/0x158 > > [ 0.486220] do_one_initcall+0x50/0x218 > > [ 0.490091] kernel_init_freeable+0x22c/0x2d0 > > [ 0.494489] kernel_init+0x18/0x110 > > [ 0.498007] ret_from_fork+0x10/0x18 > > [ 0.501614] Code: aa1403e3 91106000 97f82a27 14000011 (f940c663) > > [ 0.507770] ---[ end trace 9795948475817de4 ]--- > > [ 0.512429] Kernel panic - not syncing: Fatal exception > > [ 0.517705] Rebooting in 10 seconds.. > > > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > > Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> > > Cc: James Morse <james.morse@xxxxxxx> > > Cc: Mark Rutland <mark.rutland@xxxxxxx> > > Cc: Will Deacon <will@xxxxxxxxxx> > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > > Cc: cgroups@xxxxxxxxxxxxxxx > > Cc: linux-mm@xxxxxxxxx > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > > Cc: linux-kernel@xxxxxxxxxxxxxxx > > Cc: kexec@xxxxxxxxxxxxxxxxxxx > > Fixes: eccb52e78809 ("mm: memcontrol: prepare swap controller setup for integration") > > > Reported-by: Prabhakar Kushwaha <pkushwaha@xxxxxxxxxxx> > > Signed-off-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx> > > This is subtle as hell, I have to say. I find the ordering in the init > calls very unintuitive and extremely hard to follow. The above commit > has introduced the problem but the code previously has worked mostly by > a luck because our default was flipped. > > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > > > --- > > mm/memcontrol.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 19622328e4b5..8323e4b7b390 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -7186,6 +7186,13 @@ static struct cftype memsw_files[] = { > > { }, /* terminate */ > > }; > > > > +/* > > + * If mem_cgroup_swap_init() is implemented as a subsys_initcall() > > + * instead of a core_initcall(), this could mean cgroup_memory_noswap still > > + * remains set to false even when memcg is disabled via "cgroup_disable=memory" > > + * boot parameter. This may result in premature OOPS inside > > + * mem_cgroup_get_nr_swap_pages() function in corner cases. > > + */ > > static int __init mem_cgroup_swap_init(void) > > { > > /* No memory control -> no swap control */ > > @@ -7200,6 +7207,6 @@ static int __init mem_cgroup_swap_init(void) > > > > return 0; > > } > > -subsys_initcall(mem_cgroup_swap_init); > > +core_initcall(mem_cgroup_swap_init); > > > > #endif /* CONFIG_MEMCG_SWAP */ > > -- > > 2.7.4 > > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs
