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Subject[patch] Re: RCU?: Scheduling while atomic with 3.4.23-rt33
Date
Am Montag, 18. Februar 2013, 12:16:41 schrieb Thomas Gleixner:
> On Mon, 18 Feb 2013, Tim Sander wrote:
> > Here is a transtribed backtrace for easier reading:
> > c0010fac t dump_backtrace
> > c022c188 T dump_stack
> > c022c71c t __schedule_bug
> > c022fb28 t __schedule
> > c0230644 t rt_spin_lock_slowlock
> > c0230ba8 T rt_spin_lock
> > c003a9b8 T __wake_up
> > c0052a44 t invoke_rcu_callbacks
> > c0053764 T rcu_check_callbacks
> > c0026060 T update_process_times
>
> That's due to CONFIG_TINY_PREEMPT_RCU=y. That's a known issue, which
> has been fixed in 3.6-rt.
>
> Steven, could you backport that to 3.2/3.4 please ?
As far as i see its been the waitequeue stuff. The patch below is the patch
from 3.6. backported to 3.4.


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From 2f0eb85792045f06bc0db3fe1fff17c9298240d3 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 3 Dec 2012 16:25:21 +0100
Subject: [PATCH] rcutiny: Use simple waitqueue

Simple waitqueues can be handled from interrupt disabled contexts.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/rcutiny_plugin.h | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 97e359b..2824dbd 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -26,6 +26,7 @@
#include <linux/module.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
+#include <linux/wait-simple.h>

/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
@@ -261,7 +262,7 @@ static void show_tiny_preempt_stats(struct seq_file *m)

/* Controls for rcu_kthread() kthread. */
static struct task_struct *rcu_kthread_task;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
+static DEFINE_SWAIT_HEAD(rcu_kthread_wq);
static unsigned long have_rcu_kthread_work;

/*
@@ -754,7 +755,7 @@ void synchronize_rcu(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu);

-static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
+static DEFINE_SWAIT_HEAD(sync_rcu_preempt_exp_wq);
static unsigned long sync_rcu_preempt_exp_count;
static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);

@@ -776,7 +777,7 @@ static int rcu_preempted_readers_exp(void)
*/
static void rcu_report_exp_done(void)
{
- wake_up(&sync_rcu_preempt_exp_wq);
+ swait_wake(&sync_rcu_preempt_exp_wq);
}

/*
@@ -828,8 +829,8 @@ void synchronize_rcu_expedited(void)
else {
rcu_initiate_boost();
local_irq_restore(flags);
- wait_event(sync_rcu_preempt_exp_wq,
- !rcu_preempted_readers_exp());
+ swait_event(sync_rcu_preempt_exp_wq,
+ !rcu_preempted_readers_exp());
}

/* Clean up and exit. */
@@ -917,7 +918,7 @@ static void invoke_rcu_callbacks(void)
{
have_rcu_kthread_work = 1;
if (rcu_kthread_task != NULL)
- wake_up(&rcu_kthread_wq);
+ swait_wake(&rcu_kthread_wq);
}

#ifdef CONFIG_RCU_TRACE
@@ -947,8 +948,8 @@ static int rcu_kthread(void *arg)
unsigned long flags;

for (;;) {
- wait_event_interruptible(rcu_kthread_wq,
- have_rcu_kthread_work != 0);
+ swait_event_interruptible(rcu_kthread_wq,
+ have_rcu_kthread_work != 0);
morework = rcu_boost();
local_irq_save(flags);
work = have_rcu_kthread_work;
--
1.7.9.5
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