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Star64_linux/kernel/cgroup
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Vlastimil Babka 213980c0f2 mm, mempolicy: simplify rebinding mempolicies when updating cpusets 
Commit c0ff7453bb ("cpuset,mm: fix no node to alloc memory when
changing cpuset's mems") has introduced a two-step protocol when
rebinding task's mempolicy due to cpuset update, in order to avoid a
parallel allocation seeing an empty effective nodemask and failing.

Later, commit cc9a6c8776 ("cpuset: mm: reduce large amounts of memory
barrier related damage v3") introduced a seqlock protection and removed
the synchronization point between the two update steps.  At that point
(or perhaps later), the two-step rebinding became unnecessary.

Currently it only makes sure that the update first adds new nodes in
step 1 and then removes nodes in step 2.  Without memory barriers the
effects are questionable, and even then this cannot prevent a parallel
zonelist iteration checking the nodemask at each step to observe all
nodes as unusable for allocation.  We now fully rely on the seqlock to
prevent premature OOMs and allocation failures.

We can thus remove the two-step update parts and simplify the code.

Link: http://lkml.kernel.org/r/20170517081140.30654-5-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-06 16:24:34 -07:00
..
cgroup-internal.h cgroup: Move debug cgroup to its own file 2017-06-14 16:01:21 -04:00
cgroup-v1.c cgroup: Move debug cgroup to its own file 2017-06-14 16:01:21 -04:00
cgroup.c cgroup: implement "nsdelegate" mount option 2017-06-28 14:45:21 -04:00
cpuset.c mm, mempolicy: simplify rebinding mempolicies when updating cpusets 2017-07-06 16:24:34 -07:00
debug.c cgroup: fix lockdep warning in debug controller 2017-06-14 16:01:41 -04:00
freezer.c
Makefile cgroup: Move debug cgroup to its own file 2017-06-14 16:01:21 -04:00
namespace.c kernel: convert cgroup_namespace.count from atomic_t to refcount_t 2017-03-06 14:55:22 -05:00
pids.c cgroup/pids: remove spurious suspicious RCU usage warning 2017-03-06 15:11:29 -05:00
rdma.c