[PATCH] clk: Fix race condition between clk_set_parent and clk_enable()
skannan at codeaurora.org
Thu May 16 00:17:03 EDT 2013
On 05/15/2013 12:24 PM, Ulf Hansson wrote:
> On 1 May 2013 06:42, Saravana Kannan <skannan at codeaurora.org> wrote:
>> - /* 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.
> Looks good! Thanks for having another round to fixup this kind of
> tricky code. :-)
> Acked-by: Ulf Hansson <ulf.hansson at linaro.org>
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