Aaditya Kumar 1c7e7f6c07 mm: fix lost kswapd wakeup in kswapd_stop() ... Offlining memory may block forever, waiting for kswapd() to wake up because kswapd() does not check the event kthread->should_stop before sleeping. The proper pattern, from Documentation/memory-barriers.txt, is: --- waker --- event_indicated = 1; wake_up_process(event_daemon); --- sleeper --- for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); if (event_indicated) break; schedule(); } set_current_state() may be wrapped by: prepare_to_wait(); In the kswapd() case, event_indicated is kthread->should_stop. === offlining memory (waker) === kswapd_stop() kthread_stop() kthread->should_stop = 1 wake_up_process() wait_for_completion() === kswapd_try_to_sleep (sleeper) === kswapd_try_to_sleep() prepare_to_wait() . . schedule() . . finish_wait() The schedule() needs to be protected by a test of kthread->should_stop, which is wrapped by kthread_should_stop(). Reproducer: Do heavy file I/O in background. Do a memory offline/online in a tight loop Signed-off-by: Aaditya Kumar <aaditya.kumar@ap.sony.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2012-07-17 16:21:30 -07:00
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backing-dev.c
bootmem.c	bootmem: make ___alloc_bootmem_node_nopanic() really nopanic	2012-07-17 16:21:29 -07:00
bounce.c
cleancache.c
compaction.c
debug-pagealloc.c
dmapool.c
fadvise.c
failslab.c
filemap_xip.c
filemap.c
fremap.c
frontswap.c
highmem.c
huge_memory.c
hugetlb.c
hwpoison-inject.c
init-mm.c
internal.h
Kconfig
Kconfig.debug
kmemcheck.c
kmemleak-test.c
kmemleak.c
ksm.c
maccess.c
madvise.c
Makefile
memblock.c	memblock: free allocated memblock_reserved_regions later	2012-07-11 16:04:50 -07:00
memcontrol.c
memory_hotplug.c	mm/memory_hotplug.c: release memory resources if hotadd_new_pgdat() fails	2012-07-11 16:04:46 -07:00
memory-failure.c
memory.c
mempolicy.c
mempool.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	memblock: free allocated memblock_reserved_regions later	2012-07-11 16:04:50 -07:00
nommu.c
oom_kill.c
page_alloc.c
page_cgroup.c
page_io.c
page_isolation.c
page-writeback.c
pagewalk.c
percpu-km.c
percpu-vm.c
percpu.c
pgtable-generic.c
prio_tree.c
process_vm_access.c
quicklist.c
readahead.c
rmap.c
shmem.c	shmem: cleanup shmem_add_to_page_cache	2012-07-11 16:04:48 -07:00
slab.c
slob.c
slub.c
sparse-vmemmap.c
sparse.c	mm: sparse: fix usemap allocation above node descriptor section	2012-07-11 16:04:49 -07:00
swap_state.c
swap.c
swapfile.c
truncate.c
util.c
vmalloc.c
vmscan.c	mm: fix lost kswapd wakeup in kswapd_stop()	2012-07-17 16:21:30 -07:00
vmstat.c