lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 7 May 2012 17:57:42 -0700 From: Colin Cross <ccross@...roid.com> To: linux-kernel@...r.kernel.org Cc: linux-arm-kernel@...ts.infradead.org, linux-pm@...ts.linux-foundation.org, Kevin Hilman <khilman@...com>, Len Brown <len.brown@...el.com>, Trinabh Gupta <g.trinabh@...il.com>, Arjan van de Ven <arjan@...ux.intel.com>, Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Kay Sievers <kay.sievers@...y.org>, Santosh Shilimkar <santosh.shilimkar@...com>, Daniel Lezcano <daniel.lezcano@...aro.org>, Amit Kucheria <amit.kucheria@...aro.org>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, Arnd Bergmann <arnd.bergmann@...aro.org>, Russell King <linux@....linux.org.uk>, "Rafael J. Wysocki" <rjw@...k.pl>, Colin Cross <ccross@...roid.com> Subject: [PATCHv4 4/4] cpuidle: coupled: add parallel barrier function 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@...com> Tested-by: Santosh Shilimkar <santosh.shilimkar@...com> Reviewed-by: Kevin Hilman <khilman@...com> Tested-by: Kevin Hilman <khilman@...com> Signed-off-by: Colin Cross <ccross@...roid.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 93101fb..3e65de1 100644 --- a/drivers/cpuidle/coupled.c +++ b/drivers/cpuidle/coupled.c @@ -130,6 +130,43 @@ 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 = dev->coupled->online_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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists