mm, cpuset: always use seqlock when changing task's nodemask
authorVlastimil Babka <vbabka@suse.cz>
Thu, 6 Jul 2017 22:40:09 +0000 (15:40 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 6 Jul 2017 23:24:34 +0000 (16:24 -0700)
commit5f155f27cb7f0670429e2b8bb954094fa4110df9
tree948abdb05daa9047e1444e8d54fafb4fba153202
parent213980c0f23b6c4932fd5516da7e8443b2a615ea
mm, cpuset: always use seqlock when changing task's nodemask

When updating task's mems_allowed and rebinding its mempolicy due to
cpuset's mems being changed, we currently only take the seqlock for
writing when either the task has a mempolicy, or the new mems has no
intersection with the old mems.

This should be enough to prevent a parallel allocation seeing no
available nodes, but the optimization is IMHO unnecessary (cpuset
updates should not be frequent), and we still potentially risk issues if
the intersection of new and old nodes has limited amount of
free/reclaimable memory.

Let's just use the seqlock for all tasks.

Link: http://lkml.kernel.org/r/20170517081140.30654-6-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>
kernel/cgroup/cpuset.c