From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: mingo@kernel.org, tglx@linutronix.de, juri.lelli@arm.com,
rostedt@goodmis.org, xlpang@redhat.com,
linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com,
jdesfossez@efficios.com, bristot@redhat.com,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH -v2 1/9] rtmutex: Deboost before waking up the top waiter
Date: Wed, 28 Sep 2016 11:24:13 +0200 [thread overview]
Message-ID: <20160928092413.GN5012@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160928090740.npogdsea32etq57t@linutronix.de>
On Wed, Sep 28, 2016 at 11:07:40AM +0200, Sebastian Andrzej Siewior wrote:
> On 2016-09-26 14:32:14 [+0200], Peter Zijlstra wrote:
> > --- a/kernel/futex.c
> > +++ b/kernel/futex.c
> > @@ -1374,9 +1374,8 @@ static int wake_futex_pi(u32 __user *uad
> > * scheduled away before the wake up can take place.
> > */
> > spin_unlock(&hb->lock);
> > - wake_up_q(&wake_q);
> > - if (deboost)
> > - rt_mutex_adjust_prio(current);
> > +
> > + rt_mutex_postunlock(&wake_q, deboost);
>
> This breaks -RT. Before that spin_unlock() you do a preempt_disable()
> which means you had one spinlock with enabled preemption and now you get
> one unlock with disabled preemption. And this breaks migrate_disable() /
> enable (because we take the fast path in the in_atomic() case).
Oh crud, the hb lock is not raw :/
next prev parent reply other threads:[~2016-09-28 9:24 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 12:32 [PATCH -v2 0/9] PI and assorted failings Peter Zijlstra
2016-09-26 12:32 ` [PATCH -v2 1/9] rtmutex: Deboost before waking up the top waiter Peter Zijlstra
2016-09-26 15:15 ` Steven Rostedt
2016-09-26 15:22 ` Peter Zijlstra
2016-09-26 15:35 ` Steven Rostedt
2016-09-26 15:37 ` Steven Rostedt
2016-09-26 15:41 ` Peter Zijlstra
2016-09-29 14:43 ` Thomas Gleixner
2016-09-29 14:49 ` Peter Zijlstra
2016-09-26 15:39 ` Peter Zijlstra
2016-09-28 9:07 ` Sebastian Andrzej Siewior
2016-09-28 9:24 ` Peter Zijlstra [this message]
2016-09-26 12:32 ` [PATCH -v2 2/9] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra
2016-09-26 15:20 ` Steven Rostedt
2016-09-26 15:26 ` Peter Zijlstra
2016-09-29 14:49 ` Thomas Gleixner
2016-09-26 12:32 ` [PATCH -v2 3/9] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update Peter Zijlstra
2016-09-26 16:03 ` Steven Rostedt
2016-09-29 14:48 ` Thomas Gleixner
2016-09-26 12:32 ` [PATCH -v2 4/9] rtmutex: Remove rt_mutex_fastunlock() Peter Zijlstra
2016-09-29 14:47 ` Thomas Gleixner
2016-09-26 12:32 ` [PATCH -v2 5/9] rtmutex: Clean up Peter Zijlstra
2016-09-26 16:09 ` Steven Rostedt
2016-09-29 14:51 ` Thomas Gleixner
2016-09-26 12:32 ` [PATCH -v2 6/9] sched/rtmutex: Refactor rt_mutex_setprio() Peter Zijlstra
2016-09-26 16:57 ` Steven Rostedt
2016-09-26 12:32 ` [PATCH -v2 7/9] sched,tracing: Update trace_sched_pi_setprio() Peter Zijlstra
2016-09-26 17:04 ` Steven Rostedt
2016-09-27 7:44 ` Peter Zijlstra
2016-09-26 12:32 ` [PATCH -v2 8/9] rtmutex: Fix PI chain order integrity Peter Zijlstra
2016-09-26 12:32 ` [PATCH -v2 9/9] rtmutex: Fix more prio comparisons Peter Zijlstra
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