Messages in this thread Patch in this message | | | From | Colin Cross <> | Subject | [PATCHv3 4/5] cpuidle: coupled: add parallel barrier function | Date | Mon, 30 Apr 2012 13:09:10 -0700 |
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Adds cpuidle_coupled_parallel_barrier, which can be used by coupled cpuidle state enter functions to handle resynchronization after determining if any cpu needs to abort. The normal use case will be:
static bool abort_flag; static atomic_t abort_barrier;
int arch_cpuidle_enter(struct cpuidle_device *dev, ...) { if (arch_turn_off_irq_controller()) { /* returns an error if an irq is pending and would be lost if idle continued and turned off power */ abort_flag = true; }
cpuidle_coupled_parallel_barrier(dev, &abort_barrier);
if (abort_flag) { /* One of the cpus didn't turn off it's irq controller */ arch_turn_on_irq_controller(); return -EINTR; }
/* continue with idle */ ... }
This will cause all cpus to abort idle together if one of them needs to abort.
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Reviewed-by: Kevin Hilman <khilman@ti.com> Tested-by: Kevin Hilman <khilman@ti.com> Signed-off-by: Colin Cross <ccross@android.com> --- drivers/cpuidle/coupled.c | 37 +++++++++++++++++++++++++++++++++++++ include/linux/cpuidle.h | 4 ++++ 2 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c index d097826..242dc7c 100644 --- a/drivers/cpuidle/coupled.c +++ b/drivers/cpuidle/coupled.c @@ -134,6 +134,43 @@ struct cpuidle_coupled { static cpumask_t cpuidle_coupled_poked_mask; /** + * cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus + * @dev: cpuidle_device of the calling cpu + * @a: atomic variable to hold the barrier + * + * No caller to this function will return from this function until all online + * cpus in the same coupled group have called this function. Once any caller + * has returned from this function, the barrier is immediately available for + * reuse. + * + * The atomic variable a must be initialized to 0 before any cpu calls + * this function, will be reset to 0 before any cpu returns from this function. + * + * Must only be called from within a coupled idle state handler + * (state.enter when state.flags has CPUIDLE_FLAG_COUPLED set). + * + * Provides full smp barrier semantics before and after calling. + */ +void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a) +{ + int n = atomic_read(&dev->coupled->alive_count); + + smp_mb__before_atomic_inc(); + atomic_inc(a); + + while (atomic_read(a) < n) + cpu_relax(); + + if (atomic_inc_return(a) == n * 2) { + atomic_set(a, 0); + return; + } + + while (atomic_read(a) > n) + cpu_relax(); +} + +/** * cpuidle_state_is_coupled - check if a state is part of a coupled set * @dev: struct cpuidle_device for the current cpu * @drv: struct cpuidle_driver for the platform diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index 6038448..5ab7183 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -183,6 +183,10 @@ static inline int cpuidle_wrap_enter(struct cpuidle_device *dev, #endif +#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED +void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a); +#endif + /****************************** * CPUIDLE GOVERNOR INTERFACE * ******************************/ -- 1.7.7.3
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