Re: [PATCH 2/6] irq_work: Implement remote queueing

[Peter Zijlstra <peterz@infradead.org>]

On Wed, Jun 25, 2014 at 11:36:57AM +0200, Peter Zijlstra wrote:
> On Wed, Jun 25, 2014 at 12:07:05PM +0530, Srivatsa S. Bhat wrote:
> > I don't think irqs_disabled() is the problematic condition, since
> > hotplug_cfg() invokes irq_work_run() from CPU_DYING context (which has
> > irqs disabled). I guess you meant to remove the in_irq() check inside
> > irq_work_run() instead?
> 
> Yes, clearly I should not get up at 6am.. :-) Let me go do a new one.

---
Subject: irq_work: Remove BUG_ON in irq_work_run()
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed Jun 25 07:13:07 CEST 2014

Because of a collision with 8d056c48e486 ("CPU hotplug, smp: flush any
pending IPI callbacks before CPU offline"), which ends up calling
hotplug_cfd()->flush_smp_call_function_queue()->irq_work_run(), which
is not from IRQ context.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-busatzs2gvz4v62258agipuf@git.kernel.org
---
 kernel/irq_work.c |   12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

Index: linux-2.6/kernel/irq_work.c
===================================================================
--- linux-2.6.orig/kernel/irq_work.c
+++ linux-2.6/kernel/irq_work.c
@@ -160,21 +160,11 @@ static void irq_work_run_list(struct lli
 	}
 }
 
-static void __irq_work_run(void)
+static void irq_work_run(void)
 {
 	irq_work_run_list(&__get_cpu_var(raised_list));
 	irq_work_run_list(&__get_cpu_var(lazy_list));
 }
-
-/*
- * Run the irq_work entries on this cpu. Requires to be ran from hardirq
- * context with local IRQs disabled.
- */
-void irq_work_run(void)
-{
-	BUG_ON(!in_irq());
-	__irq_work_run();
-}
 EXPORT_SYMBOL_GPL(irq_work_run);
 
 /*