synchronize_irq() waits for hard irq and threaded handlers to complete before returning. For some special cases we only need to make sure that the hard interrupt part of the irq line is not in progress when we disabled the - possibly shared - interrupt at the device level. A proper use case for this was provided by Russell. The sdhci driver requires some irq triggered functions to be run in thread context. The current implementation of the thread context is a sdio private kthread construct, which has quite some shortcomings. These can be avoided when the thread is directly associated to the device interrupt via the generic threaded irq infrastructure. Though there is a corner case related to run time power management where one side disables the device interrupts at the device level and needs to make sure, that an already running hard interrupt handler has completed before proceeding further. Though that hard interrupt handler might wake the associated thread, which in turn can request the runtime PM to reenable the device. Using synchronize_irq() leads to an immediate deadlock of the irq thread waiting for the PM lock and the synchronize_irq() waiting for the irq thread to complete. Due to the fact that it is sufficient for this case to ensure that no hard irq handler is executing a new function which avoids the check for the thread is required. Add a function, which just monitors the hard irq parts and ignores the threaded handlers. Signed-off-by: Thomas Gleixner --- include/linux/hardirq.h | 1 kernel/irq/manage.c | 67 +++++++++++++++++++++++++++++++++--------------- 2 files changed, 48 insertions(+), 20 deletions(-) Index: linux-2.6/include/linux/hardirq.h =================================================================== --- linux-2.6.orig/include/linux/hardirq.h +++ linux-2.6/include/linux/hardirq.h @@ -9,6 +9,7 @@ extern void synchronize_irq(unsigned int irq); +extern void synchronize_hardirq(unsigned int irq); #if defined(CONFIG_TINY_RCU) Index: linux-2.6/kernel/irq/manage.c =================================================================== --- linux-2.6.orig/kernel/irq/manage.c +++ linux-2.6/kernel/irq/manage.c @@ -32,24 +32,10 @@ static int __init setup_forced_irqthread early_param("threadirqs", setup_forced_irqthreads); #endif -/** - * synchronize_irq - wait for pending IRQ handlers (on other CPUs) - * @irq: interrupt number to wait for - * - * This function waits for any pending IRQ handlers for this interrupt - * to complete before returning. If you use this function while - * holding a resource the IRQ handler may need you will deadlock. - * - * This function may be called - with care - from IRQ context. - */ -void synchronize_irq(unsigned int irq) +static void __synchronize_hardirq(struct irq_desc *desc) { - struct irq_desc *desc = irq_to_desc(irq); bool inprogress; - if (!desc) - return; - do { unsigned long flags; @@ -67,12 +53,53 @@ void synchronize_irq(unsigned int irq) /* Oops, that failed? */ } while (inprogress); +} - /* - * We made sure that no hardirq handler is running. Now verify - * that no threaded handlers are active. - */ - wait_event(desc->wait_for_threads, !atomic_read(&desc->threads_active)); +/** + * synchronize_hardirq - wait for pending hard IRQ handlers (on other CPUs) + * @irq: interrupt number to wait for + * + * This function waits for any pending hard IRQ handlers for this + * interrupt to complete before returning. If you use this + * function while holding a resource the IRQ handler may need you + * will deadlock. It does not take associated threaded handlers into + * account. + * + * This function may be called - with care - from IRQ context. + */ +void synchronize_hardirq(unsigned int irq) +{ + struct irq_desc *desc = irq_to_desc(irq); + + if (desc) + __synchronize_hardirq(desc); +} +EXPORT_SYMBOL(synchronize_hardirq); + +/** + * synchronize_irq - wait for pending IRQ handlers (on other CPUs) + * @irq: interrupt number to wait for + * + * This function waits for any pending IRQ handlers for this interrupt + * to complete before returning. If you use this function while + * holding a resource the IRQ handler may need you will deadlock. + * + * This function may be called - with care - from IRQ context. + */ +void synchronize_irq(unsigned int irq) +{ + struct irq_desc *desc = irq_to_desc(irq); + + if (desc) { + __synchronize_hardirq(desc); + /* + * We made sure that no hardirq handler is + * running. Now verify that no threaded handlers are + * active. + */ + wait_event(desc->wait_for_threads, + !atomic_read(&desc->threads_active)); + } } EXPORT_SYMBOL(synchronize_irq); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/