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From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] MAX1111: Fix race condition causing NULL pointer exception
Date: Wed, 18 May 2011 16:29:35 +0100	[thread overview]
Message-ID: <20110518152935.GJ5913@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1305731918-20164-1-git-send-email-morpheus.ibis@gmail.com>

On Wed, May 18, 2011 at 05:18:38PM +0200, Pavel Herrmann wrote:
> spi_sync call uses its spi_message parameter to keep completion information,
> having this structure static is not thread-safe, potentially causing one
> thread having pointers to memory on or above other threads stack. use
> per-call spi_message on stack to fix this

I assume this has not been tested with DMA debugging enabled.

The DMA API does not like mapping memory from the stack, which is what
you're potentially doing with this:

> +	uint8_t rx_buf[2] = {0, 0};
> +	uint8_t tx_buf = (channel << MAX1111_CTRL_SEL_SH) |
> +			MAX1111_CTRL_PD0 | MAX1111_CTRL_PD1 |
> +			MAX1111_CTRL_SGL | MAX1111_CTRL_UNI |
> +			MAX1111_CTRL_STR;
> +
> +	spi_message_init(&m);
> +	memset(t, 0, sizeof(t));
> +
> +	t[0].tx_buf = &tx_buf;
> +	t[0].len = 1;
> +	spi_message_add_tail(&t[0], &m);
> +
> +	t[1].rx_buf = rx_buf;
> +	t[1].len = 2;
> +	spi_message_add_tail(&t[1], &m);

  parent reply	other threads:[~2011-05-18 15:29 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-18 15:18 Pavel Herrmann
2011-05-18 15:29 ` Eric Miao
2011-05-18 15:29 ` Russell King - ARM Linux [this message]
2011-05-18 17:36   ` Marek Vasut
2011-05-18 22:47     ` Russell King - ARM Linux
2011-05-19 12:35   ` Pavel Machek
2011-05-19 12:51     ` Pavel Herrmann
2011-05-19 13:55       ` Marek Vasut
2011-05-19 19:31       ` Russell King - ARM Linux
2011-05-19 22:13         ` Pavel Herrmann
2011-05-20 21:20           ` Russell King - ARM Linux
2011-05-21 20:28           ` Pavel Machek
2011-05-21 20:45             ` Pavel Herrmann
2011-05-22 15:52               ` Marek Vasut
2011-05-18 21:47 ` Cyril Hrubis
2011-06-30 12:36   ` Marek Vasut

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