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Groups > linux.kernel > #1385183
| From | Wolfram Sang <wsa@the-dreams.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 2/2] i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared |
| Date | 2016-04-22 15:40 +0200 |
| Message-ID | <rqJtp-2Ga-31@gated-at.bofh.it> (permalink) |
| References | <roJxw-4hm-1@gated-at.bofh.it> <roJxw-4hm-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
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On Sat, Apr 16, 2016 at 09:14:53PM -0400, Javier Martinez Canillas wrote: > The exynos5 I2C controller driver always prepares and enables a clock > before using it and then disables unprepares it when the clock is not > used anymore. > > But this can cause a possible ABBA deadlock in some scenarios since a > driver that uses regmap to access its I2C registers, will first grab > the regmap lock and then the I2C xfer function will grab the prepare > lock when preparing the I2C clock. But since the clock driver also > uses regmap for I2C accesses, preparing a clock will first grab the > prepare lock and then the regmap lock when using the regmap API. > > An example of this happens on the Exynos5422 Odroid XU4 board where a > s2mps11 PMIC is used and both the s2mps11 regulators and clk drivers > share the same I2C regmap. > > The possible deadlock is reported by the kernel lockdep: > > Possible unsafe locking scenario: > > CPU0 CPU1 Squashed both patches into one for easier backporting, added stable and applied to for-current, thanks!
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[PATCH v2 1/2] i2c: exynos5: Check clk_prepare_enable() return value Javier Martinez Canillas <javier@osg.samsung.com> - 2016-04-17 03:20 +0200
[PATCH v2 2/2] i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared Javier Martinez Canillas <javier@osg.samsung.com> - 2016-04-17 03:20 +0200
Re: [PATCH v2 2/2] i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared Krzysztof Kozlowski <k.kozlowski@samsung.com> - 2016-04-17 15:40 +0200
Re: [PATCH v2 2/2] i2c: exynos5: Fix possible ABBA deadlock by keeping I2C clock prepared Wolfram Sang <wsa@the-dreams.de> - 2016-04-22 15:40 +0200
Re: [PATCH v2 1/2] i2c: exynos5: Check clk_prepare_enable() return value Krzysztof Kozlowski <k.kozlowski@samsung.com> - 2016-04-17 15:40 +0200
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