linux-kernel - Re: [PATCH AUTOSEL 5.4 6/8] clk: Don't hold prepare_lock when calling kref

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Message-ID: <cc21ff5ddd8fbe07e75fdffd596c0aa1.sboyd@kernel.org>
Date: Tue, 23 Apr 2024 12:24:51 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Douglas Anderson <dianders@...omium.org>, Sasha Levin <sashal@...nel.org>, mturquette@...libre.com, linux-clk@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.4 6/8] clk: Don't hold prepare_lock when calling kref_put()

Quoting Sasha Levin (2024-04-23 04:03:01)
> From: Stephen Boyd <sboyd@...nel.org>
> 
> [ Upstream commit 6f63af7511e7058f3fa4ad5b8102210741c9f947 ]
> 
> We don't need to hold the prepare_lock when dropping a ref on a struct
> clk_core. The release function is only freeing memory and any code with
> a pointer reference has already unlinked anything pointing to the
> clk_core. This reduces the holding area of the prepare_lock a bit.
> 
> Note that we also don't call free_clk() with the prepare_lock held.
> There isn't any reason to do that.

You'll want the patch before this, 8358a76cfb47 ("clk: Remove
prepare_lock hold assertion in __clk_release()"), to avoid lockdep
warnings. And it looks like the problem was reported on v5.15.y so all
5 patches from the series would need a backport.

 8358a76cfb47 clk: Remove prepare_lock hold assertion in __clk_release()
 6f63af7511e7 clk: Don't hold prepare_lock when calling kref_put()
 9d05ae531c2c clk: Initialize struct clk_core kref earlier
 e581cf5d2162 clk: Get runtime PM before walking tree during disable_unused
 9d1e795f754d clk: Get runtime PM before walking tree for clk_summary