percpu: fix synchronization between synchronous map extension and chunk destruction

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[ Upstream commit 6710e594f7 ]

For non-atomic allocations, pcpu_alloc() can try to extend the area
map synchronously after dropping pcpu_lock; however, the extension
wasn't synchronized against chunk destruction and the chunk might get
freed while extension is in progress.

This patch fixes the bug by putting most of non-atomic allocations
under pcpu_alloc_mutex to synchronize against pcpu_balance_work which
is responsible for async chunk management including destruction.

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>
Cc: stable@vger.kernel.org # v3.18+
Fixes: 1a4d76076c ("percpu: implement asynchronous chunk population")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

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Tejun Heo 2016-05-25 11:48:25 -04:00 • committed by Sasha Levin

parent d273823dc6

commit 62f7175fa6

1 changed files with 8 additions and 8 deletions

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mm/percpu.c

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