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i2c: at91: Fix a race condition during signal handling in at91_do_twi_xfer.

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There is a race condition in at91_do_twi_xfer when signals arrive.
If a signal is recieved while waiting for a transfer to complete
wait_for_completion_interruptible_timeout() will return -ERESTARTSYS.
This is not handled correctly resulting in interrupts still being
enabled and a transfer being in flight when we return.

Symptoms include a range of oopses and bus lockups. Oopses can happen
when the transfer completes because the interrupt handler will corrupt
the stack. If a new transfer is started before the interrupt fires
the controller will start a new transfer in the middle of the old one,
resulting in confused slaves and a locked bus.

To avoid this, use wait_for_completion_io_timeout instead so that we
don't have to deal with gracefully shutting down the transfer and
disabling the interrupts.

Signed-off-by: Simon Lindgren <simon@aqwary.com>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org
This commit is contained in:
Simon Lindgren 2014-08-26 21:13:24 +02:00 committed by Wolfram Sang
parent 0ce4bc1dbd
commit 6721f28a26
1 changed files with 2 additions and 2 deletions
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4
drivers/i2c/busses/i2c-at91.c
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@ -421,8 +421,8 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
}
}
ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
dev->adapter.timeout);
ret = wait_for_completion_io_timeout(&dev->cmd_complete,
dev->adapter.timeout);
if (ret == 0) {
dev_err(dev->dev, "controller timed out\n");
at91_init_twi_bus(dev);