[PATCH] clk: rockchip: fix deadlock possibility in cpuclk

Mike Turquette
2015-01-17T19:23:29Z

Quoting Doug Anderson (2015-01-16 09:11:06)
> Heiko,
>
> On Fri, Jan 16, 2015 at 8:52 AM, Heiko St?bner <heiko@sntech.de> wrote:
> > Lockdep reported a possible deadlock between the cpuclk lock and for example
> > the i2c driver.
> >
> > CPU0 CPU1
> > ---- ----
> > lock(clk_lock);
> > local_irq_disable();
> > lock(&(&i2c->lock)->rlock);
> > lock(clk_lock);
> > <Interrupt>
> > lock(&(&i2c->lock)->rlock);
> >
> > *** DEADLOCK ***
> >
> > The generic clock-types of the core ccf already use spin_lock_irqsave when
> > touching clock registers, so do the same for the cpuclk.
> >
> > Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> > ---
> > drivers/clk/rockchip/clk-cpu.c | 10 ++++++----
> > 1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/clk/rockchip/clk-cpu.c b/drivers/clk/rockchip/clk-cpu.c
> > index 75c8c45..3ecdf7d 100644
> > --- a/drivers/clk/rockchip/clk-cpu.c
> > +++ b/drivers/clk/rockchip/clk-cpu.c
> > @@ -124,10 +124,11 @@ static int rockchip_cpuclk_pre_rate_change(struct rockchip_cpuclk *cpuclk,
> > {
> > const struct rockchip_cpuclk_reg_data *reg_data = cpuclk->reg_data;
> > unsigned long alt_prate, alt_div;
> > + unsigned long flags = 0;
>
> nit: I don't often see flags initted to 0 here when using
> spin_lock_irqsave(). I don't think it's needed...
>
> I doubt it really matters though, and this looks fine to me.
>
> Reviewed-by: Doug Anderson <dianders@chromium.org>

Applied to clk-fixes and removed flags initialization locally.

Regards,
Mike

>
> -Doug