From: Tomeu Vizoso <tomeu.vizoso@collabora.com> To: Stephen Boyd <sboyd@codeaurora.org>, Mike Turquette <mturquette@linaro.org> Cc: Stephen Warren <swarren@wwwdotorg.org>, Peter De Schrijver <pdeschrijver@nvidia.com>, linux-kernel@vger.kernel.org, tomasz.figa@gmail.com, rabin@rab.in, Thierry Reding <thierry.reding@gmail.com>, Javier Martinez Canillas <javier.martinez@collabora.co.uk>, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v9 5/6] clk: Add floor and ceiling constraints to clock rates Date: Thu, 04 Sep 2014 15:34:57 +0200 [thread overview] Message-ID: <54086A81.1060606@collabora.com> (raw) In-Reply-To: <5407A6B9.1080606@codeaurora.org> On 09/04/2014 01:39 AM, Stephen Boyd wrote: > On 09/03/14 08:33, Tomeu Vizoso wrote: >> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index 61a3492..3a961c6 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -560,6 +560,8 @@ struct clk *__clk_create_clk(struct clk_core *clk_core, const char *dev, >> clk->dev_id = dev; >> clk->con_id = con; >> >> + hlist_add_head(&clk->child_node, &clk_core->per_user_clks); >> + > > How is this safe with another thread that may be traversing the list? Or > even two threads calling clk_get_parent() at the same time? Good point, will take the prepare lock. >> +int clk_set_floor_rate(struct clk *clk_user, unsigned long rate) >> +{ >> + struct clk_core *clk = clk_to_clk_core(clk_user); >> + >> + clk_user->floor_constraint = rate; >> + return clk_provider_set_rate(clk, clk_provider_get_rate(clk)); > > It would be nice if this was also locked around so that the > floor_constraint or ceiling_constraint doesn't change while another > thread is iterating the list. I guess we'll get by though because > eventually things will settle and either this thread here will set the > "final" rate, or the other thread in clk_provider_set_rate() will have > already set the final rate. It just seems wrong to not hold the lock > while updating what is supposed to be protected by the prepare lock. Yeah, I also lean towards having an explicit lock, as having a more deterministic behaviour can be quite helpful when debugging. Thanks, Tomeu
WARNING: multiple messages have this Message-ID (diff)
From: tomeu.vizoso@collabora.com (Tomeu Vizoso) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v9 5/6] clk: Add floor and ceiling constraints to clock rates Date: Thu, 04 Sep 2014 15:34:57 +0200 [thread overview] Message-ID: <54086A81.1060606@collabora.com> (raw) In-Reply-To: <5407A6B9.1080606@codeaurora.org> On 09/04/2014 01:39 AM, Stephen Boyd wrote: > On 09/03/14 08:33, Tomeu Vizoso wrote: >> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index 61a3492..3a961c6 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -560,6 +560,8 @@ struct clk *__clk_create_clk(struct clk_core *clk_core, const char *dev, >> clk->dev_id = dev; >> clk->con_id = con; >> >> + hlist_add_head(&clk->child_node, &clk_core->per_user_clks); >> + > > How is this safe with another thread that may be traversing the list? Or > even two threads calling clk_get_parent() at the same time? Good point, will take the prepare lock. >> +int clk_set_floor_rate(struct clk *clk_user, unsigned long rate) >> +{ >> + struct clk_core *clk = clk_to_clk_core(clk_user); >> + >> + clk_user->floor_constraint = rate; >> + return clk_provider_set_rate(clk, clk_provider_get_rate(clk)); > > It would be nice if this was also locked around so that the > floor_constraint or ceiling_constraint doesn't change while another > thread is iterating the list. I guess we'll get by though because > eventually things will settle and either this thread here will set the > "final" rate, or the other thread in clk_provider_set_rate() will have > already set the final rate. It just seems wrong to not hold the lock > while updating what is supposed to be protected by the prepare lock. Yeah, I also lean towards having an explicit lock, as having a more deterministic behaviour can be quite helpful when debugging. Thanks, Tomeu
next prev parent reply other threads:[~2014-09-04 13:35 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-09-03 15:29 [PATCH v9 0/6] Per-user clock constraints Tomeu Vizoso 2014-09-03 15:29 ` Tomeu Vizoso 2014-09-03 15:29 ` [PATCH v9 1/6] clk: Add temporary mapping to the existing API Tomeu Vizoso 2014-09-03 15:29 ` Tomeu Vizoso 2014-09-03 15:31 ` [PATCH v9 2/6] clk: Move all drivers to use internal API Tomeu Vizoso 2014-09-03 15:31 ` Tomeu Vizoso 2014-09-08 6:13 ` Mike Turquette 2014-09-08 6:13 ` Mike Turquette 2014-09-09 6:15 ` Mike Turquette 2014-09-03 15:33 ` [PATCH v9 3/6] clk: use struct clk only for external API Tomeu Vizoso 2014-09-03 15:33 ` Tomeu Vizoso 2014-09-03 15:33 ` [PATCH v9 4/6] clk: per-user clock accounting for debug Tomeu Vizoso 2014-09-03 15:33 ` Tomeu Vizoso 2014-09-03 15:33 ` [PATCH v9 5/6] clk: Add floor and ceiling constraints to clock rates Tomeu Vizoso 2014-09-03 15:33 ` Tomeu Vizoso 2014-09-03 23:39 ` Stephen Boyd 2014-09-03 23:39 ` Stephen Boyd 2014-09-04 0:53 ` Mike Turquette 2014-09-04 0:53 ` Mike Turquette 2014-09-04 8:53 ` Tomeu Vizoso 2014-09-04 8:53 ` Tomeu Vizoso 2014-09-04 13:34 ` Tomeu Vizoso [this message] 2014-09-04 13:34 ` Tomeu Vizoso 2014-09-03 15:33 ` [PATCH v9 6/6] clk: Warn of unbalanced clk_prepare() calls Tomeu Vizoso 2014-09-03 15:33 ` Tomeu Vizoso 2014-09-03 17:26 ` [PATCH v9 0/6] Per-user clock constraints Mike Turquette 2014-09-04 8:30 ` Tomeu Vizoso 2014-09-04 8:30 ` Tomeu Vizoso
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