[Skiboot] [PATCH] p8-i2c: Fix race between OCC interrupt and recovery timer

[Stewart Smith]

Oliver O'Halloran <oohall at gmail.com> writes:
> When we request ownership of an I2C bus from the OCC we wait until the
> OCC notifies us the bus is available with an interrupt. The wait time is
> limited by the recovery timer duration which will cancel the pending
> transaction if the OCC takes too long to hand ownership of the bus to
> OPAL.
>
> There is a race between the timeout function and the OCC interrupt
> handler which can result in a deadlock when the two are run
> concurrently. If both are running and the OCC interrupt aquires
> the I2C master lock first it will wait attempt to cancel the recovery
> timer which waits for the timeout handler function to finish if it's
> already running. The problem is that the recovery handler will also
> attempt to aquire the I2C master lock which results in both threads
> waiting for each other to finish.
>
> Fix this by using cancel_timer_async() which doesn not wait for the
> timeout handle function to finish running.
>
> Reported-by: Anton Blanchard <anton at samba.org>
> Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
> ---
>  hw/p8-i2c.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Merged the one Anton sent (exactly the same patch) as of
4466a6ec89bf39afeb98b92d03bbf7fc30c55afe


-- 
Stewart Smith
OPAL Architect, IBM.