percpu: fix synchronization between chunk->map_extend_work and chunk destruction

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commit 4f996e234d upstream.

Atomic allocations can trigger async map extensions which is serviced
by chunk->map_extend_work.  pcpu_balance_work which is responsible for
destroying idle chunks wasn't synchronizing properly against
chunk->map_extend_work and may end up freeing the chunk while the work
item is still in flight.

This patch fixes the bug by rolling async map extension operations
into pcpu_balance_work.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Fixes: 9c824b6a17 ("percpu: make sure chunk->map array has available space")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Tejun Heo 2016-05-25 11:48:25 -04:00 • committed by Greg Kroah-Hartman

parent 0da3127a76

commit c26ae537f1

1 changed files with 36 additions and 21 deletions

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mm/percpu.c

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