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Message-ID: <20200523150831.wdrthklakwm6wago@linutronix.de>
Date: Sat, 23 May 2020 17:08:31 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Will Deacon <will@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Lai Jiangshan <jiangshanlai@...il.com>,
Josh Triplett <josh@...htriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
rcu@...r.kernel.org
Subject: Re: [PATCH 3/8] srcu: Use local_lock() for per-CPU struct srcu_data
access
On 2020-05-22 10:39:53 [-0700], Paul E. McKenney wrote:
> It looks good to me, but I have not yet tested it. (Happy to let you
> take the first crack at rcutorture in any case, scenarios SRCU-P and
> SRCU-N.)
on it.
> > That check_init_srcu_struct() is needed, because otherwise:
> >
> > | BUG: spinlock bad magic on CPU#2, swapper/0/1
> > | lock: 0xffff88803ed28ac0, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
> > | CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc6+ #81
> > | Call Trace:
> > | dump_stack+0x71/0xa0
> > | do_raw_spin_lock+0x6c/0xb0
> > | _raw_spin_lock_irqsave+0x33/0x40
> > | synchronize_srcu+0x24/0xc9
> > | wakeup_source_remove+0x4d/0x70
> > | wakeup_source_unregister.part.0+0x9/0x40
> > | device_wakeup_enable+0x99/0xc0
> >
> > I'm not sure if there should be an explicit init of `wakeup_srcu' or if
> > an srcu function (like call_srcu()) is supposed to do it.
>
> It is fine. Beforehand, that check_init_srcu_struct() would have been
> invoked very shortly thereafter from __call_srcu(), and there is no
> instead harm invoking it a few microseconds earlier. ;-)
Oki. I wasn't sure if an explizit initialized on wakeup_srcu's side was
missing or if this is new since we use the lock earlier.
> Thanx, Paul
Sebastian
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