Re: [PATCH] clk: Fix race condition between clk_set_parent and clk_enable()

[Saravana Kannan]

On 05/15/2013 12:24 PM, Ulf Hansson wrote:
> On 1 May 2013 06:42, Saravana Kannan <skannan@xxxxxxxxxxxxxx> wrote:

<snip>

> > -       /* migrate prepare */
> > -       if (clk->prepare_count)
> > +       /*
> > +        * Migrate prepare state between parents and prevent race with
> > +        * clk_enable().
> > +        *
> > +        * If the clock is not prepared, then a race with
> > +        * clk_enable/disable() is impossible since we already have the
> > +        * prepare lock (future calls to clk_enable() need to be preceded by
> > +        * a clk_prepare()).
> > +        *
> > +        * If the clock is prepared, migrate the prepared state to the new
> > +        * parent and also protect against a race with clk_enable() by
> > +        * forcing the clock and the new parent on.  This ensures that all
> > +        * future calls to clk_enable() are practically NOPs with respect to
> > +        * hardware and software states.
> > +        */
>
> Maybe an additional note about that since CLK_SET_PARENT_GATE is a
> prerequisite for doing migration of "prepare", we also interpreted
> this flags as it is acceptable to enable the clock(s) in this context.

Done. Sent v2 patch.

<snip>

> Looks good! Thanks for having another round to fixup this kind of
> tricky code. :-)

Thanks :-)

> Acked-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>

Thanks again.

-Saravana

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