On Mon, Aug 19, 2013 at 10:17 PM, Neil Zhang <zhan...@marvell.com> wrote:
> There is a corener case when no peripheral irqs route to secondary
> cores.
> Let's take dual core system for example, the sequence is as following:
>
> Core 0 Core1
> 1. set waiting bit and enter waiting loop
> 2. set waiting bit and poke core1
> 3. clear poke in irq and enter safe state
> 4. set ready bit and enter ready loop
>
> Since there is no peripheral irq route to core 1, so it will stay in
> safe state forever, and core 0 will dead loop in the following code.
> while (!cpuidle_coupled_cpus_ready(coupled)) {
> /* Check if any other cpus bailed out of idle. */
> if (!cpuidle_coupled_cpus_waiting(coupled))
> }
>
> The solution is don't let secondary core enter safe state when it has
> already handled the poke interrupt.
>
> Signed-off-by: Neil Zhang <zhan...@marvell.com>
> Reviewed-by: Fangsuo Wu <f...@marvell.com>
> ---
> drivers/cpuidle/coupled.c | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c
> index 2a297f8..a37c718 100644
> --- a/drivers/cpuidle/coupled.c
> +++ b/drivers/cpuidle/coupled.c
> @@ -119,6 +119,7 @@ struct cpuidle_coupled {
> #define CPUIDLE_COUPLED_NOT_IDLE (-1)
>
> static DEFINE_MUTEX(cpuidle_coupled_lock);
> +static DEFINE_PER_CPU(bool, poke_sync);
> static DEFINE_PER_CPU(struct call_single_data, cpuidle_coupled_poke_cb);
>
> /*
> @@ -295,6 +296,7 @@ static void cpuidle_coupled_poked(void *info)
> {
> int cpu = (unsigned long)info;
> cpumask_clear_cpu(cpu, &cpuidle_coupled_poked_mask);
> + __this_cpu_write(poke_sync, true);
> }
>
> /**
> @@ -473,6 +475,7 @@ retry:
> * allowed for a single cpu.
> */
> while (!cpuidle_coupled_cpus_waiting(coupled)) {
> + __this_cpu_write(poke_sync, false);
> if (cpuidle_coupled_clear_pokes(dev->cpu)) {
> cpuidle_coupled_set_not_waiting(dev->cpu, coupled);
> goto out;
> @@ -483,6 +486,10 @@ retry:
> goto out;
> }
>
> + if (cpuidle_coupled_cpus_waiting(coupled)
> + && __this_cpu_read(poke_sync))
> + break;
> +
> entered_state = cpuidle_enter_state(dev, drv,
> dev->safe_state_index);
> }
> --
> 1.7.4.1
>
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I have a similar patch that avoids adding another check for
cpuidle_coupled_cpus_waiting, and uses the return value from
cpuidle_coupled_clear_pokes instead of adding a percpu bool. I will
post it shortly.
Do you have a test case that can reproduce this easily?
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