Michal Hocko 751e5f5c75 vmstat: allocate vmstat_wq before it is used ... kernel test robot has reported the following crash: BUG: unable to handle kernel NULL pointer dereference at 00000100 IP: [<c1074df6>] __queue_work+0x26/0x390 *pdpt = 0000000000000000 *pde = f000ff53f000ff53 *pde = f000ff53f000ff53 Oops: 0000 [#1] PREEMPT PREEMPT SMP SMP CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted 4.4.0-rc4-00139-g373ccbe #1 Workqueue: events vmstat_shepherd task: cb684600 ti: cb7ba000 task.ti: cb7ba000 EIP: 0060:[<c1074df6>] EFLAGS: 00010046 CPU: 0 EIP is at __queue_work+0x26/0x390 EAX: 00000046 EBX: cbb37800 ECX: cbb37800 EDX: 00000000 ESI: 00000000 EDI: 00000000 EBP: cb7bbe68 ESP: cb7bbe38 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 CR0: 8005003b CR2: 00000100 CR3: 01fd5000 CR4: 000006b0 Stack: Call Trace: __queue_delayed_work+0xa1/0x160 queue_delayed_work_on+0x36/0x60 vmstat_shepherd+0xad/0xf0 process_one_work+0x1aa/0x4c0 worker_thread+0x41/0x440 kthread+0xb0/0xd0 ret_from_kernel_thread+0x21/0x40 The reason is that start_shepherd_timer schedules the shepherd work item which uses vmstat_wq (vmstat_shepherd) before setup_vmstat allocates that workqueue so if the further initialization takes more than HZ we might end up scheduling on a NULL vmstat_wq. This is really unlikely but not impossible. Fixes: 373ccbe592 ("mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make any progress") Reported-by: kernel test robot <ying.huang@linux.intel.com> Signed-off-by: Michal Hocko <mhocko@suse.com> Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: stable@vger.kernel.org Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2016-01-08 23:47:54 -08:00
..
kasan
backing-dev.c	mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make any progress	2015-12-12 10:15:34 -08:00
balloon_compaction.c
bootmem.c
cleancache.c
cma_debug.c
cma.c
cma.h
compaction.c
debug-pagealloc.c
debug.c
dmapool.c
early_ioremap.c
fadvise.c
failslab.c
filemap.c
frame_vector.c
frontswap.c
gup.c
highmem.c
huge_memory.c
hugetlb_cgroup.c
hugetlb.c	mm/hugetlb.c: fix resv map memory leak for placeholder entries	2015-12-12 10:15:34 -08:00
hwpoison-inject.c
init-mm.c
internal.h
interval_tree.c
Kconfig
Kconfig.debug
kmemcheck.c
kmemleak-test.c
kmemleak.c
ksm.c
list_lru.c
maccess.c
madvise.c
Makefile
memblock.c
memcontrol.c	mm: memcontrol: fix possible memcg leak due to interrupted reclaim	2015-12-29 17:45:49 -08:00
memory_hotplug.c	mm/memory_hotplug.c: check for missing sections in test_pages_in_a_zone()	2015-12-29 17:45:49 -08:00
memory-failure.c
memory.c
mempolicy.c
mempool.c
memtest.c
migrate.c
mincore.c
mlock.c
mm_init.c
mmap.c
mmu_context.c
mmu_notifier.c
mmzone.c
mprotect.c
mremap.c
msync.c
nobootmem.c
nommu.c
oom_kill.c	mm/oom_kill.c: avoid attempting to kill init sharing same memory	2015-12-12 10:15:34 -08:00
page_alloc.c	mm: fix swapped Movable and Reclaimable in /proc/pagetypeinfo	2015-12-12 10:15:34 -08:00
page_counter.c
page_ext.c
page_idle.c
page_io.c
page_isolation.c
page_owner.c
page-writeback.c
pagewalk.c
percpu-km.c
percpu-vm.c
percpu.c
pgtable-generic.c
process_vm_access.c
quicklist.c
readahead.c
rmap.c
shmem.c	tmpfs: fix shmem_evict_inode() warnings on i_blocks	2015-12-12 10:15:34 -08:00
slab_common.c
slab.c
slab.h
slob.c
slub.c
sparse-vmemmap.c
sparse.c
swap_cgroup.c
swap_state.c
swap.c
swapfile.c
truncate.c
userfaultfd.c
util.c
vmacache.c
vmalloc.c
vmpressure.c
vmscan.c
vmstat.c	vmstat: allocate vmstat_wq before it is used	2016-01-08 23:47:54 -08:00
workingset.c
zbud.c
zpool.c
zsmalloc.c
zswap.c	mm/zswap: change incorrect strncmp use to strcmp	2015-12-18 14:25:40 -08:00