From patchwork Tue Sep 22 23:55:47 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Heiko Stuebner X-Patchwork-Id: 7246531 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 3A1A9BEEC1 for ; Tue, 22 Sep 2015 23:56:03 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 38A73205D3 for ; Tue, 22 Sep 2015 23:56:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E85320588 for ; Tue, 22 Sep 2015 23:56:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934153AbbIVXz7 (ORCPT ); Tue, 22 Sep 2015 19:55:59 -0400 Received: from gloria.sntech.de ([95.129.55.99]:44072 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935115AbbIVXzy (ORCPT ); Tue, 22 Sep 2015 19:55:54 -0400 Received: from ip5f5b95ad.dynamic.kabel-deutschland.de ([95.91.149.173] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1ZeXPX-0006iv-Qb; Wed, 23 Sep 2015 01:55:47 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: mturquette@baylibre.com, sboyd@codeaurora.org, Kevin Hilman , "Rafael J. Wysocki" , Pavel Machek Cc: Caesar Wang , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: [PATCH v2] clk: readd refcounting for struct clk instances Date: Wed, 23 Sep 2015 01:55:47 +0200 Message-ID: <6257096.h7pub3XnDQ@diego> User-Agent: KMail/4.14.10 (Linux/4.1.0-2-amd64; KDE/4.14.10; x86_64; ; ) MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP With the split into struct clk and struct clk_core, clocks lost the ability for nested __clk_get clkdev calls. While it stays possible to call __clk_get, the first call to (__)clk_put will clear the struct clk, making subsequent clk_put calls run into a NULL pointer dereference. One prime example of this sits in the generic power domain code, where it is possible to add the clocks both by name and by passing in a struct clk via pm_clk_add_clk(). __pm_clk_add() in turn then calls __clk_get to increase the refcount, so that the original code can put the clock again. A possible call-path looks like clk = of_clk_get(); pm_clk_add_clk(dev, clk); clk_put(clk); with pm_clk_add_clk() => __pm_clk_add() then calling __clk_get on the clk and later clk_put when the pm clock list gets destroyed, thus creating a NULL pointer deref, as the struct clk doesn't exist anymore. So add a separate refcounting for struct clk instances and only clean up once the refcount reaches zero. This makes it possible again to hand off a clock reference to common code without needing to track it further. Signed-off-by: Heiko Stuebner --- While it may be nice to do the actual handling of the clock references only in the calling code, in this current use case it would create a big additional overhead. It looks like this so called synchronous reset on power-domain state- changes, requiring device clocks to be turned on, is not that uncommon or rockchip-specific. For this Kevin requested that we read the clocks from the actual consumer devices and not double-list them in the power-domain node as well. So when expecting pm_clk_add_clk() to work, the current powerdomain code can simply do when adding a device to a domain in rockchip_pd_attach_dev(): while ((clk = of_clk_get(dev->of_node, i++)) && !IS_ERR(clk)) { dev_dbg(dev, "adding clock '%pC' to list of PM clocks\n", clk); error = pm_clk_add_clk(dev, clk); clk_put(clk); } The clock gets handed off to the generic pm clock handling and thus clk_put in there. On the other hand when only the rockchip power-domain code is expected to get and put the clock, we would require a lot of new overhead, as now the code would also need to track which devices got added to what domain and also all clock-references until the device gets detached again. So this would essentially duplicate a big part of what the genpd-code does (per-domain device-list and per-device clock-list). As this seems to be not uncommon, future powerdomain drivers might need that too and would also need to duplicate that handling. When allowing multiple __clk_get and __clk_put calls on the other hand, the overhead for the regular case comes down to one atomic_inc, atomic_sub_and_test and the function call to the new separate release function ;-) . changes in v2: removed double parentheses found by Stephen Boyd drivers/clk/clk.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 43e2c3a..7aab1a4 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -85,6 +85,7 @@ struct clk { unsigned long min_rate; unsigned long max_rate; struct hlist_node clks_node; + struct kref ref; }; /*** locking ***/ @@ -2590,7 +2591,7 @@ fail_out: EXPORT_SYMBOL_GPL(clk_register); /* Free memory allocated for a clock. */ -static void __clk_release(struct kref *ref) +static void __clk_core_release(struct kref *ref) { struct clk_core *core = container_of(ref, struct clk_core, ref); int i = core->num_parents; @@ -2606,6 +2607,18 @@ static void __clk_release(struct kref *ref) kfree(core); } +static void __clk_release(struct kref *ref) +{ + struct clk *clk = container_of(ref, struct clk, ref); + + hlist_del(&clk->clks_node); + if (clk->min_rate > clk->core->req_rate || + clk->max_rate < clk->core->req_rate) + clk_core_set_rate_nolock(clk->core, clk->core->req_rate); + + kfree(clk); +} + /* * Empty clk_ops for unregistered clocks. These are used temporarily * after clk_unregister() was called on a clock and until last clock @@ -2684,7 +2697,7 @@ void clk_unregister(struct clk *clk) if (clk->core->prepare_count) pr_warn("%s: unregistering prepared clock: %s\n", __func__, clk->core->name); - kref_put(&clk->core->ref, __clk_release); + kref_put(&clk->core->ref, __clk_core_release); clk_prepare_unlock(); } @@ -2759,12 +2772,14 @@ int __clk_get(struct clk *clk) return 0; kref_get(&core->ref); + kref_get(&clk->ref); } return 1; } void __clk_put(struct clk *clk) { + struct clk_core *core; struct module *owner; if (!clk || WARN_ON_ONCE(IS_ERR(clk))) @@ -2772,19 +2787,15 @@ void __clk_put(struct clk *clk) clk_prepare_lock(); - hlist_del(&clk->clks_node); - if (clk->min_rate > clk->core->req_rate || - clk->max_rate < clk->core->req_rate) - clk_core_set_rate_nolock(clk->core, clk->core->req_rate); + core = clk->core; + owner = core->owner; - owner = clk->core->owner; - kref_put(&clk->core->ref, __clk_release); + kref_put(&clk->ref, __clk_release); + kref_put(&core->ref, __clk_core_release); clk_prepare_unlock(); module_put(owner); - - kfree(clk); } /*** clk rate change notifiers ***/