Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754734Ab3IXVi4 (ORCPT ); Tue, 24 Sep 2013 17:38:56 -0400 Received: from mail-ee0-f51.google.com ([74.125.83.51]:58542 "EHLO mail-ee0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750877Ab3IXViy (ORCPT ); Tue, 24 Sep 2013 17:38:54 -0400 Message-ID: <52420664.2040604@gmail.com> Date: Tue, 24 Sep 2013 23:38:44 +0200 From: Sylwester Nawrocki User-Agent: Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20120412 Thunderbird/11.0.1 MIME-Version: 1.0 To: linux@arm.linux.org.uk, mturquette@linaro.org CC: Sylwester Nawrocki , linux-arm-kernel@lists.infradead.org, jiada_wang@mentor.com, kyungmin.park@samsung.com, myungjoo.ham@samsung.com, t.figa@samsung.com, g.liakhovetski@gmx.de, laurent.pinchart@ideasonboard.com, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org Subject: Re: [PATCH v6 0/5] clk: clock deregistration support References: <1377874402-2944-1-git-send-email-s.nawrocki@samsung.com> In-Reply-To: <1377874402-2944-1-git-send-email-s.nawrocki@samsung.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8783 Lines: 279 On 08/30/2013 04:53 PM, Sylwester Nawrocki wrote: > This patch series implements clock deregistration in the common clock > framework. Comparing to v5 it only includes further corrections of NULL > clock handling. [...] > clk: Provide not locked variant of of_clk_get_from_provider() > clkdev: Fix race condition in clock lookup from device tree > clk: Add common __clk_get(), __clk_put() implementations > clk: Assign module owner of a clock being registered > clk: Implement clk_unregister Hi Mike, Russell, Would you have any further comments/suggestions on this series ? I have inspected all callers of clk_register() and all should be fine with regards to dereferencing dev->driver. The first argument to this function is either NULL or clk_register() is being called in drivers' probe() callback, which ensures dev->driver won't change due to holding dev->mutex. The only issue I found might be at the omap3isp driver, which provides clock to its sub-drivers and takes reference on the sub-driver modules. When sub-driver calls clk_get() all modules would get locked in memory, due to circular reference. One solution to that could be to pass NULL struct device pointer, as in the below patch. ---------8<------------------ From ca5963041aad67e31324cb5d4d5e2cfce1706d4f Mon Sep 17 00:00:00 2001 From: Sylwester Nawrocki Date: Thu, 19 Sep 2013 23:52:04 +0200 Subject: [PATCH] omap3isp: Pass NULL device pointer to clk_register() Signed-off-by: Sylwester Nawrocki --- drivers/media/platform/omap3isp/isp.c | 15 ++++++++++----- drivers/media/platform/omap3isp/isp.h | 1 + 2 files changed, 11 insertions(+), 5 deletions(-) diff --git a/drivers/media/platform/omap3isp/isp.c b/drivers/media/platform/omap3isp/isp.c index df3a0ec..d7f3c98 100644 --- a/drivers/media/platform/omap3isp/isp.c +++ b/drivers/media/platform/omap3isp/isp.c @@ -290,9 +290,11 @@ static int isp_xclk_init(struct isp_device *isp) struct clk_init_data init; unsigned int i; + for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) + isp->xclks[i] = ERR_PTR(-EINVAL); + for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) { struct isp_xclk *xclk = &isp->xclks[i]; - struct clk *clk; xclk->isp = isp; xclk->id = i == 0 ? ISP_XCLK_A : ISP_XCLK_B; @@ -306,9 +308,9 @@ static int isp_xclk_init(struct isp_device *isp) xclk->hw.init = &init; - clk = devm_clk_register(isp->dev, &xclk->hw); - if (IS_ERR(clk)) - return PTR_ERR(clk); + xclk->clk = clk_register(NULL, &xclk->hw); + if (IS_ERR(xclk->clk)) + return PTR_ERR(xclk->clk); if (pdata->xclks[i].con_id == NULL && pdata->xclks[i].dev_id == NULL) @@ -320,7 +322,7 @@ static int isp_xclk_init(struct isp_device *isp) xclk->lookup->con_id = pdata->xclks[i].con_id; xclk->lookup->dev_id = pdata->xclks[i].dev_id; - xclk->lookup->clk = clk; + xclk->lookup->clk = xclk->clk; clkdev_add(xclk->lookup); } @@ -335,6 +337,9 @@ static void isp_xclk_cleanup(struct isp_device *isp) for (i = 0; i < ARRAY_SIZE(isp->xclks); ++i) { struct isp_xclk *xclk = &isp->xclks[i]; + if (!IS_ERR(xclk->clk)) + clk_unregister(xclk->clk); + if (xclk->lookup) clkdev_drop(xclk->lookup); } diff --git a/drivers/media/platform/omap3isp/isp.h b/drivers/media/platform/omap3isp/isp.h index cd3eff4..1498f2b 100644 --- a/drivers/media/platform/omap3isp/isp.h +++ b/drivers/media/platform/omap3isp/isp.h @@ -135,6 +135,7 @@ struct isp_xclk { struct isp_device *isp; struct clk_hw hw; struct clk_lookup *lookup; + struct clk *clk; enum isp_xclk_id id; spinlock_t lock; /* Protects enabled and divider */ -- ---------8<------------------ Alternatively an additional argument could be added to the clk_register*() functions. Something like: ---------8<------------------ diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 27f8c42..ef934ac 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1837,7 +1837,8 @@ struct clk *__clk_register(struct device *dev, struct clk_hw *hw) } EXPORT_SYMBOL_GPL(__clk_register); -static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk) +static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk, + struct module *owner) { int i, ret; @@ -1877,6 +1878,8 @@ static int _clk_register(struct device *dev, struct clk_hw *hw, struct clk *clk) } } + clk->owner = owner; + ret = __clk_init(dev, clk); if (!ret) return 0; @@ -1892,7 +1895,7 @@ fail_name: } /** - * clk_register - allocate a new clock, register it and return an opaque cookie + * ___clk_register - allocate a new clock, register it and return an opaque cookie * @dev: device that is registering this clock * @hw: link to hardware-specific clock data * @@ -1902,7 +1905,8 @@ fail_name: * rest of the clock API. In the event of an error clk_register will return an * error code; drivers must test for an error code after calling clk_register. */ -struct clk *clk_register(struct device *dev, struct clk_hw *hw) +struct clk *___clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner) { int ret; struct clk *clk; @@ -1914,7 +1918,7 @@ struct clk *clk_register(struct device *dev, struct clk_hw *hw) goto fail_out; } - ret = _clk_register(dev, hw, clk); + ret = _clk_register(dev, hw, clk, owner); if (!ret) return clk; @@ -1922,7 +1926,7 @@ struct clk *clk_register(struct device *dev, struct clk_hw *hw) fail_out: return ERR_PTR(ret); } -EXPORT_SYMBOL_GPL(clk_register); +EXPORT_SYMBOL_GPL(___clk_register); /* * Free memory allocated for a clock. @@ -2040,7 +2044,8 @@ static void devm_clk_release(struct device *dev, void *res) * automatically clk_unregister()ed on driver detach. See clk_register() for * more information. */ -struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw) +struct clk *__devm_clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner) { struct clk *clk; int ret; @@ -2049,7 +2054,7 @@ struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw) if (!clk) return ERR_PTR(-ENOMEM); - ret = _clk_register(dev, hw, clk); + ret = _clk_register(dev, hw, clk, owner); if (!ret) { devres_add(dev, clk); } else { @@ -2059,7 +2064,7 @@ struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw) return clk; } -EXPORT_SYMBOL_GPL(devm_clk_register); +EXPORT_SYMBOL_GPL(__devm_clk_register); static int devm_clk_match(struct device *dev, void *res, void *data) { diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index 13623f3..c656ebf 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -31,6 +31,7 @@ #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */ struct clk_hw; +struct module; /** * struct clk_ops - Callback operations for hardware clocks; these are to @@ -436,8 +437,21 @@ struct clk *clk_register_composite(struct device *dev, const char *name, * rest of the clock API. In the event of an error clk_register will return an * error code; drivers must test for an error code after calling clk_register. */ -struct clk *clk_register(struct device *dev, struct clk_hw *hw); -struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw); +struct clk *___clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner); + +static inline struct clk *clk_register(struct device *dev, struct clk_hw *hw) +{ + return ___clk_register(dev, hw, THIS_MODULE); +} + +struct clk *__devm_clk_register(struct device *dev, struct clk_hw *hw, + struct module *owner); +static inline struct clk *devm_clk_register(struct device *dev, + struct clk_hw *hw) +{ + return __devm_clk_register(dev, hw, THIS_MODULE); +} void clk_unregister(struct clk *clk); void devm_clk_unregister(struct device *dev, struct clk *clk); ---------8<------------------ Similarly it would need to be done for the remaining clk_register*() functions, which have much longer arguments list. It's a bit messy, since there is already __clk_register() function with double underscore prefix. Perhaps that could be renamed to something else so all the functions taking struct module * parameter are prefixed with double underscore. I would squash patches 3/5 and 4/5 in the next iteration, if it is decided to keep using dev->driver->owner. -- Thanks, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/