Attachment 208491 Details for Bug 245535 – Patch to not run a softirq from a hardirq directly

Patch to not run a softirq from a hardirq directly

dont-run-softirq-in-hardirq.patch (text/x-patch), 2.71 KB, created by Clark Williams on 2007-09-27 14:17:02 UTC

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Creator: Clark Williams

Created: 2007-09-27 14:17:02 UTC

Size: 2.71 KB

patch

obsolete

>Index: linux-2.6.21-rt-hack/kernel/irq/manage.c
>===================================================================
>--- linux-2.6.21-rt-hack.orig/kernel/irq/manage.c
>+++ linux-2.6.21-rt-hack/kernel/irq/manage.c
>@@ -761,17 +761,9 @@ static int do_irqd(void * __desc)
> 	struct irq_desc *desc = __desc;
> 
> #ifdef CONFIG_SMP
>-	cpumask_t cpus_allowed, mask;
>-	int pinned_cpu;
>+	cpumask_t cpus_allowed;
> 
> 	cpus_allowed = desc->affinity;
>-	/*
>-	 * Restrict it to one cpu so we avoid being migrated inside of
>-	 * do_softirq_from_hardirq()
>-	 */
>-	pinned_cpu = first_cpu(desc->affinity);
>-	mask = cpumask_of_cpu(pinned_cpu);
>-	set_cpus_allowed(current, mask);
> #endif
> 	current->flags |= PF_NOFREEZE | PF_HARDIRQ;
> 
>@@ -795,16 +787,9 @@ static int do_irqd(void * __desc)
> 		/*
> 		 * Did IRQ affinities change?
> 		 */
>-		if (!cpu_isset(pinned_cpu, desc->affinity)) {
>+		if (!cpus_equal(cpus_allowed, desc->affinity)) {
> 			cpus_allowed = desc->affinity;
>-			/*
>-			 * Restrict it to one cpu so we avoid being
>-			 * migrated inside of
>-			 * do_softirq_from_hardirq()
>-			 */
>-			pinned_cpu = first_cpu(desc->affinity);
>-			mask = cpumask_of_cpu(pinned_cpu);
>-			set_cpus_allowed(current, mask);
>+			set_cpus_allowed(current, cpus_allowed);
> 		}
> #endif
> 		schedule();
>Index: linux-2.6.21-rt-hack/kernel/softirq.c
>===================================================================
>--- linux-2.6.21-rt-hack.orig/kernel/softirq.c
>+++ linux-2.6.21-rt-hack/kernel/softirq.c
>@@ -28,6 +28,26 @@
> #include <linux/tick.h>
> 
> #include <asm/irq.h>
>+
>+#ifdef CONFIG_SMP
>+/*
>+ * There's too many races to do this right now.
>+ *
>+ * First, a hard irq thread can migrate to other CPUS.
>+ *  That would hurt the softirq function.
>+ *
>+ * Second, if we try to pin the IRQ thread to a CPU while
>+ *  it runs the softirq. We in essence will disable the IRQ
>+ *  if a higher priority process comes in and preempts it.
>+ *  So, even if the IRQ's affinity is fine for other CPUs
>+ *  it will need to wait for the High priority task to
>+ *  release the CPU to let the IRQ thread to finish.
>+ *
>+ * On Uniprocessor, it's fine to do.
>+ */
>+#define DISABLE_SOFTIRQ_FROM_HARDIRQ 1
>+#endif
>+
> /*
>    - No shared variables, all the data are CPU local.
>    - If a softirq needs serialization, let it serialize itself
>@@ -102,7 +122,8 @@ static void wakeup_softirqd(int softirq)
> 
> 	if (unlikely(!tsk))
> 		return;
>-#if 1
>+
>+#ifndef DISABLE_SOFTIRQ_FROM_HARDIRQ
> #if defined(CONFIG_PREEMPT_SOFTIRQS) && defined(CONFIG_PREEMPT_HARDIRQS)
> 	/*
> 	 * Optimization: if we are in a hardirq thread context, and
>@@ -412,6 +433,10 @@ void do_softirq_from_hardirq(void)
> {
> 	unsigned long p_flags;
> 
>+#ifdef DISABLE_SOFTIRQ_FROM_HARDIRQ
>+	return;
>+#endif
>+
> 	/*
> 	 * 'immediate' softirq execution, from hardirq context:
> 	 */

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Attachments on bug 245535: 208481 | 208491