From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Jan Kara <jack@suse.cz>
Cc: LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Mel Gorman <mgorman@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Waiman Long <longman@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: Crash with PREEMPT_RT on aarch64 machine
Date: Mon, 7 Nov 2022 18:12:53 +0100 [thread overview]
Message-ID: <Y2k8lZNZ4/XuUm8K@linutronix.de> (raw)
In-Reply-To: <20221107163016.cnzhknmdnhajfxdh@quack3>
On 2022-11-07 17:30:16 [+0100], Jan Kara wrote:
> On Mon 07-11-22 16:10:34, Sebastian Andrzej Siewior wrote:
> > + locking, arm64
> >
> > On 2022-11-07 14:56:36 [+0100], Jan Kara wrote:
> > > > spinlock_t and raw_spinlock_t differ slightly in terms of locking.
> > > > rt_spin_lock() has the fast path via try_cmpxchg_acquire(). If you
> > > > enable CONFIG_DEBUG_RT_MUTEXES then you would force the slow path which
> > > > always acquires the rt_mutex_base::wait_lock (which is a raw_spinlock_t)
> > > > while the actual lock is modified via cmpxchg.
> > >
> > > So I've tried enabling CONFIG_DEBUG_RT_MUTEXES and indeed the corruption
> > > stops happening as well. So do you suspect some bug in the CPU itself?
> >
> > If it is only enabling CONFIG_DEBUG_RT_MUTEXES (and not whole lockdep)
> > then it looks very suspicious.
>
> Just to confirm, CONFIG_DEBUG_RT_MUTEXES is the only thing I've enabled and
> the list corruption disappeared.
I don't know if this works but:
if you tell task_struct_cachep to be created with SLAB_CACHE_DMA32 then
the pointer should only have the lower 32bit set. With this could make
rt_mutex_base::owner an atomic_t type. You could then replace
try_cmpxchg_acquire() with atomic_try_cmpxchg_acquire() and do the 32bit
cmpxchg. You would then need set the const upper 32bit of the pointer
while returning the pointer.
I have no idea how much sense it makes but you would avoid the 64bit
cmpxchg making those two a little more alike :)
> Honza
>
Sebastian
next prev parent reply other threads:[~2022-11-07 17:13 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-03 11:54 Crash with PREEMPT_RT on aarch64 machine Jan Kara
2022-11-04 16:30 ` Sebastian Andrzej Siewior
2022-11-07 13:56 ` Jan Kara
2022-11-07 15:10 ` Sebastian Andrzej Siewior
2022-11-07 16:30 ` Jan Kara
2022-11-07 17:12 ` Sebastian Andrzej Siewior [this message]
2022-11-07 16:49 ` Waiman Long
2022-11-08 10:53 ` Mark Rutland
2022-11-08 17:45 ` Jan Kara
2022-11-09 9:55 ` Mark Rutland
2022-11-09 10:11 ` Pierre Gondois
2022-11-09 10:54 ` Jan Kara
2022-11-09 11:01 ` Jan Kara
2022-11-09 13:52 ` Pierre Gondois
2022-11-09 14:21 ` Pierre Gondois
2022-11-09 12:57 ` Will Deacon
2022-11-09 15:40 ` Jan Kara
2022-11-11 14:27 ` Jan Kara
2022-11-14 12:41 ` Will Deacon
2022-11-28 15:58 ` Sebastian Andrzej Siewior
2022-11-28 20:30 ` kernel test robot
2022-11-28 21:11 ` kernel test robot
2022-11-29 5:16 ` kernel test robot
2022-11-29 5:26 ` kernel test robot
2022-11-29 6:48 ` kernel test robot
2022-11-29 7:39 ` kernel test robot
2022-11-30 17:20 ` Pierre Gondois
2022-12-01 12:37 ` Jan Kara
2022-11-30 20:22 ` Mel Gorman
2022-12-01 17:09 ` Mel Gorman
[not found] ` <20221104080637.626-1-hdanton@sina.com>
2022-11-07 12:41 ` Jan Kara
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