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From: Peter Zijlstra <peterz@infradead.org>
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	rostedt@goodmis.org
Cc: mingo@kernel.org, joel@joelfernandes.org,
	gregkh@linuxfoundation.org, gustavo@embeddedor.com,
	tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org,
	mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
	luto@kernel.org, tony.luck@intel.com, frederic@kernel.org,
	dan.carpenter@oracle.com, mhiramat@kernel.org
Subject: Re: [PATCH v4 16/27] tracing: Remove regular RCU context for _rcuidle tracepoints (again)
Date: Fri, 6 Mar 2020 11:43:35 +0100	[thread overview]
Message-ID: <20200306104335.GF3348@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20200221134216.051596115@infradead.org>

On Fri, Feb 21, 2020 at 02:34:32PM +0100, Peter Zijlstra wrote:
> Effectively revert commit 865e63b04e9b2 ("tracing: Add back in
> rcu_irq_enter/exit_irqson() for rcuidle tracepoints") now that we've
> taught perf how to deal with not having an RCU context provided.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>  include/linux/tracepoint.h |    8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -179,10 +179,8 @@ static inline struct tracepoint *tracepo
>  		 * For rcuidle callers, use srcu since sched-rcu	\
>  		 * doesn't work from the idle path.			\
>  		 */							\
> -		if (rcuidle) {						\
> +		if (rcuidle)						\
>  			__idx = srcu_read_lock_notrace(&tracepoint_srcu);\
> -			rcu_irq_enter_irqsave();			\
> -		}							\
>  									\
>  		it_func_ptr = rcu_dereference_raw((tp)->funcs);		\
>  									\
> @@ -194,10 +192,8 @@ static inline struct tracepoint *tracepo
>  			} while ((++it_func_ptr)->func);		\
>  		}							\
>  									\
> -		if (rcuidle) {						\
> -			rcu_irq_exit_irqsave();				\
> +		if (rcuidle)						\
>  			srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\
> -		}							\
>  									\
>  		preempt_enable_notrace();				\
>  	} while (0)

So what happens when BPF registers for these tracepoints? BPF very much
wants RCU on AFAIU.

  reply	other threads:[~2020-03-06 10:44 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-21 13:34 [PATCH v4 00/27] tracing vs world Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 01/27] lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions Peter Zijlstra
2020-02-21 15:08   ` Steven Rostedt
2020-02-21 20:25     ` Peter Zijlstra
2020-02-21 20:28       ` Steven Rostedt
2020-02-21 22:01       ` Frederic Weisbecker
2020-02-22  3:08   ` Joel Fernandes
2020-02-24 10:10     ` Peter Zijlstra
2020-02-25  2:12       ` Joel Fernandes
2020-03-20 12:58   ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 02/27] hardirq/nmi: Allow nested nmi_enter() Peter Zijlstra
2020-02-21 22:21   ` Frederic Weisbecker
2020-02-24 12:13     ` Petr Mladek
2020-02-25  1:30       ` Frederic Weisbecker
2020-02-24 16:13     ` Peter Zijlstra
2020-02-25  3:09       ` Frederic Weisbecker
2020-02-25 15:41         ` Peter Zijlstra
2020-02-25 16:21           ` Frederic Weisbecker
2020-02-25 22:10           ` Frederic Weisbecker
2020-02-27  9:10             ` Peter Zijlstra
2020-02-27 13:34               ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 03/27] x86/entry: Flip _TIF_SIGPENDING and _TIF_NOTIFY_RESUME handling Peter Zijlstra
2020-02-21 16:14   ` Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 04/27] x86/mce: Delete ist_begin_non_atomic() Peter Zijlstra
2020-02-21 19:07   ` Andy Lutomirski
2020-02-21 23:40   ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 05/27] x86: Replace ist_enter() with nmi_enter() Peter Zijlstra
2020-02-21 19:05   ` Andy Lutomirski
2020-02-21 20:22     ` Peter Zijlstra
2020-02-24 10:43       ` Peter Zijlstra
2020-02-24 16:27         ` Steven Rostedt
2020-02-24 16:34           ` Peter Zijlstra
2020-02-24 16:47             ` Steven Rostedt
2020-02-24 21:31               ` Peter Zijlstra
2020-02-24 22:02                 ` Steven Rostedt
2020-02-26 10:25                   ` Peter Zijlstra
2020-02-26 13:16                     ` Peter Zijlstra
2020-02-26 10:27                   ` Peter Zijlstra
2020-02-26 15:20                     ` Steven Rostedt
2020-03-07  1:53                     ` Masami Hiramatsu
2020-02-21 13:34 ` [PATCH v4 06/27] x86/doublefault: Remove memmove() call Peter Zijlstra
2020-02-21 19:10   ` Andy Lutomirski
2020-02-21 13:34 ` [PATCH v4 07/27] rcu: Make RCU IRQ enter/exit functions rely on in_nmi() Peter Zijlstra
2020-02-26  0:23   ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 08/27] rcu/kprobes: Comment why rcu_nmi_enter() is marked NOKPROBE Peter Zijlstra
2020-02-26  0:27   ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 09/27] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-21 20:21   ` Steven Rostedt
2020-02-24 10:24     ` Peter Zijlstra
2020-02-26  0:35   ` Frederic Weisbecker
2020-02-21 13:34 ` [PATCH v4 10/27] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 11/27] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-03-06 11:50   ` Peter Zijlstra
2020-03-06 12:40     ` Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 12/27] sched,rcu,tracing: Avoid tracing before in_nmi() is correct Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 13/27] x86,tracing: Add comments to do_nmi() Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 14/27] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 15/27] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 16/27] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-03-06 10:43   ` Peter Zijlstra [this message]
2020-03-06 11:31     ` Peter Zijlstra
2020-03-06 15:51       ` Alexei Starovoitov
2020-03-06 16:04         ` Mathieu Desnoyers
2020-03-06 17:55           ` Steven Rostedt
2020-03-06 18:45             ` Joel Fernandes
2020-03-06 18:59               ` Steven Rostedt
2020-03-06 19:14                 ` Joel Fernandes
2020-03-06 20:22             ` Mathieu Desnoyers
2020-03-06 20:45               ` Steven Rostedt
2020-03-06 20:55                 ` Mathieu Desnoyers
2020-03-06 21:06                   ` Steven Rostedt
2020-03-06 23:10                   ` Alexei Starovoitov
2020-03-06 17:21         ` Joel Fernandes
2020-02-21 13:34 ` [PATCH v4 17/27] perf,tracing: Allow function tracing when !RCU Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 18/27] x86/int3: Ensure that poke_int3_handler() is not traced Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 19/27] locking/atomics, kcsan: Add KCSAN instrumentation Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 20/27] asm-generic/atomic: Use __always_inline for pure wrappers Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 21/27] asm-generic/atomic: Use __always_inline for fallback wrappers Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 22/27] compiler: Simple READ/WRITE_ONCE() implementations Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 23/27] locking/atomics: Flip fallbacks and instrumentation Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 24/27] x86/int3: Avoid atomic instrumentation Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 25/27] lib/bsearch: Provide __always_inline variant Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 26/27] x86/int3: Inline bsearch() Peter Zijlstra
2020-02-21 13:34 ` [PATCH v4 27/27] x86/int3: Ensure that poke_int3_handler() is not sanitized Peter Zijlstra
2020-02-23 19:36   ` kbuild test robot

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