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From: Steven Rostedt <rostedt@goodmis.org>
To: Joel Fernandes <joelaf@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Byungchul Park <byungchul.park@lge.com>,
	Ingo Molnar <mingo@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Glexiner <tglx@linutronix.de>,
	Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage
Date: Wed, 8 Aug 2018 08:46:29 -0400	[thread overview]
Message-ID: <20180808084629.3290d1d6@gandalf.local.home> (raw)
In-Reply-To: <CAJWu+oqPUuF4rFOQ8=G3+ZxXJxiiNRBYE8C=zZ93A8qA+muHEg@mail.gmail.com>

On Tue, 7 Aug 2018 20:53:54 -0700
Joel Fernandes <joelaf@google.com> wrote:


> > When I talked to Paul few months ago about SRCU from NMI context, he
> > mentioned the per-cpu memory operations during srcu_read_lock can be
> > NMI interrupted, that's why we added that warning.  
> 
> So I looked more closely, __srcu_read_lock on 2 different handles may
> still be doing a this_cpu_inc on the same location..
> (sp->sda->srcu_lock_count). :-(
> 
> Paul any ideas on how to solve this?
> 
> It does start to seem like a show stopper :-(

What's wrong with a this_cpu_inc()? It's atomic for the CPU. Although
it wont be atomic for the capture of the idx. But I also don't see
interrupts being disabled, thus an NMI is no different than any
interrupt doing the same thing, right?

-- Steve

  parent reply	other threads:[~2018-08-08 12:46 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-30 22:24 [PATCH v12 0/3] tracing: Centralize preemptirq tracepoints and unify their usage Joel Fernandes
2018-07-30 22:24 ` [PATCH v12 1/3] lockdep: use this_cpu_ptr instead of get_cpu_var stats Joel Fernandes
2018-07-30 22:24 ` [PATCH v12 2/3] tracepoint: Make rcuidle tracepoint callers use SRCU Joel Fernandes
2018-07-30 23:10   ` Steven Rostedt
2018-08-10 15:35   ` Steven Rostedt
2018-08-10 16:32     ` Steven Rostedt
2018-07-30 22:24 ` [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage Joel Fernandes
2018-08-06 19:50   ` Steven Rostedt
2018-08-07  0:43     ` Joel Fernandes
2018-08-07  1:43       ` Steven Rostedt
2018-08-07 13:33         ` Joel Fernandes
2018-08-07 13:49           ` Steven Rostedt
2018-08-07 14:10             ` Joel Fernandes
2018-08-07 14:34               ` Steven Rostedt
2018-08-07 14:48                 ` Joel Fernandes
2018-08-07 15:09                   ` Steven Rostedt
2018-08-07 15:24                     ` Joel Fernandes
2018-08-07 23:45                       ` Steven Rostedt
2018-08-07 23:54                         ` Joel Fernandes
2018-08-08  0:48                           ` Steven Rostedt
2018-08-08  1:17                             ` Joel Fernandes
2018-08-08  1:55                               ` Steven Rostedt
2018-08-08  2:13                                 ` Joel Fernandes
2018-08-08  2:28                                   ` Steven Rostedt
2018-08-08  3:44                                     ` Joel Fernandes
2018-08-08  3:53                                       ` Joel Fernandes
2018-08-08  5:06                                         ` Joel Fernandes
2018-08-08 12:46                                         ` Steven Rostedt [this message]
2018-08-08 13:03                                           ` Paul E. McKenney
2018-08-08 13:07                                             ` Steven Rostedt
2018-08-08 14:33                                               ` Paul E. McKenney
2018-08-08 14:49                                                 ` Steven Rostedt
2018-08-08 15:05                                                   ` Paul E. McKenney
2018-08-08 15:23                                                     ` Steven Rostedt
2018-08-08 16:02                                                       ` Paul E. McKenney
2018-08-08 16:24                                                         ` Steven Rostedt
2018-08-08 17:21                                                           ` Paul E. McKenney
2018-08-08 13:00                                         ` Paul E. McKenney
2018-08-08 14:10                                           ` Joel Fernandes
2018-08-08 14:49                                             ` Paul E. McKenney
2018-08-08 19:24                                               ` Joel Fernandes
2018-08-08 20:18                                                 ` Paul E. McKenney
2018-08-08 22:15                                                   ` Joel Fernandes
2018-08-08 22:47                                                     ` Paul E. McKenney
2018-08-09 12:18                                                       ` joel
2018-08-08 14:27                                           ` Steven Rostedt
2018-08-08 14:42                                             ` Paul E. McKenney
2018-08-08 15:27                                               ` Steven Rostedt
2018-08-08 16:03                                                 ` Paul E. McKenney
2018-08-02 14:55 ` [PATCH v12 0/3] " Masami Hiramatsu
2018-08-03  2:57   ` Joel Fernandes
2018-08-03  7:23     ` Masami Hiramatsu
2018-08-04  4:51       ` Joel Fernandes
2018-08-05 16:46         ` Joel Fernandes
2018-08-06  2:07           ` Masami Hiramatsu
2018-08-06 15:24             ` Joel Fernandes
2018-08-03  7:34     ` Masami Hiramatsu

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