On Wed, Jul 02, 2014 at 12:59:04PM +0200, Tomasz Figa wrote: > Hi All, > > While testing linux-next (next-20140625) on Exynos4412-based TRATS2 > board, from time to time I hit a deadlock between clk_disable_unused() > of Common Clock Framework and parallel clk_prepare() from s3c24xx-i2c > driver. > > I believe the following is happening (in processes 1 and 2): > 1: clk_disable_unused() > 1: clk_prepare_lock() > 1: mutex_lock(clk prepare mutex) // lock A > 1: max77686_clk_is_prepared() > 1: regmap_read() > 2: regulator_set_voltage() > 2: regmap_read() > 2: mutex_lock(max77686 regmap mutex) // lock B > 2: i2c_transfer() > 2: s3c24xx_i2c_xfer() > 2: clk_unprepare() > 2: clk_prepare_lock() > 2: mutex_lock(clk prepare mutex) // lock A > 1: mutex_lock(max77686 regmap mutex) // lock B > 1,2: BOOM! > > I suppose this is a general problem affecting any MFD device that is > also a clock provider, but I clearly don't have a good idea what to do > about it. > Or if you use notifiers which use i2c... See also http://comments.gmane.org/gmane.linux.kernel/1553699. One workaround is to always leave the clock of the i2c controller in a prepared state. Cheers, Peter. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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