Alexey Kardashevskiy 19c12f1209 powerpc/powernv/ioda: Fix race in TCE level allocation
commit 56090a3902 upstream.

pnv_tce() returns a pointer to a TCE entry and originally a TCE table
would be pre-allocated. For the default case of 2GB window the table
needs only a single level and that is fine. However if more levels are
requested, it is possible to get a race when 2 threads want a pointer
to a TCE entry from the same page of TCEs.

This adds cmpxchg to handle the race. Note that once TCE is non-zero,
it cannot become zero again.

Fixes: a68bd1267b ("powerpc/powernv/ioda: Allocate indirect TCE levels on demand")
CC: stable@vger.kernel.org # v4.19+
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190718051139.74787-2-aik@ozlabs.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-10-11 18:20:50 +02:00
2019-10-07 18:57:24 +02:00
2019-10-07 18:57:29 +02:00

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