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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
Carsten Emde <C.Emde@osadl.org>, Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH 07/16] softirq: Fix nohz pending issue for real
Date: Wed, 13 Feb 2013 17:12:02 +0100
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From: Thomas Gleixner <tglx@linutronix.de>
We really need to iterate through all softirqs to find a potentially
blocked runner.
T1 runs softirq X (that cleared pending bit for X)
Interrupt raises softirq Y
T1 gets blocked on a lock and lock owner is not runnable
T1 schedules out
CPU goes idle and complains about pending softirq Y.
Now iterating over all softirqs lets us find the runner for X and
eliminate Y from the to warn about list as well.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/softirq.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)
Index: linux-3.2.35-rt53/kernel/softirq.c
===================================================================
@ linux-3.2.35-rt53/kernel/softirq.c:103 @ void softirq_check_pending_idle(void)
{
static int rate_limit;
struct softirq_runner *sr = &__get_cpu_var(softirq_runners);
- u32 warnpending, pending = local_softirq_pending();
+ u32 warnpending = local_softirq_pending();
+ int i;
if (rate_limit >= 10)
return;
- warnpending = pending;
+ for (i = 0; i < NR_SOFTIRQS; i++) {
+ struct task_struct *tsk = sr->runner[i];
- while (pending) {
- struct task_struct *tsk;
- int i = __ffs(pending);
-
- pending &= ~(1 << i);
-
- tsk = sr->runner[i];
/*
* The wakeup code in rtmutex.c wakes up the task
* _before_ it sets pi_blocked_on to NULL under