From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
Brian Gerst <brgerst@gmail.com>, Juergen Gross <JGross@suse.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code
Date: Sun, 01 Mar 2020 19:12:25 +0100 [thread overview]
Message-ID: <878skkeygm.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrVNcpoubrpVrtGjXSQrod8jzjweszEPX_WSJM747xr8wQ@mail.gmail.com>
Andy Lutomirski <luto@kernel.org> writes:
> On Sun, Mar 1, 2020 at 7:21 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>> Andy Lutomirski <luto@amacapital.net> writes:
>> >> On Mar 1, 2020, at 2:16 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> >> Ok, but for the time being anything before/after CONTEXT_KERNEL is unsafe
>> >> except trace_hardirq_off/on() as those trace functions do not allow to
>> >> attach anything AFAICT.
>> >
>> > Can you point to whatever makes those particular functions special? I
>> > failed to follow the macro maze.
>>
>> Those are not tracepoints and not going through the macro maze. See
>> kernel/trace/trace_preemptirq.c
>
> That has:
>
> void trace_hardirqs_on(void)
> {
> if (this_cpu_read(tracing_irq_cpu)) {
> if (!in_nmi())
> trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
> this_cpu_write(tracing_irq_cpu, 0);
> }
>
> lockdep_hardirqs_on(CALLER_ADDR0);
> }
> EXPORT_SYMBOL(trace_hardirqs_on);
> NOKPROBE_SYMBOL(trace_hardirqs_on);
>
> But this calls trace_irq_enable_rcuidle(), and that's the part of the
> macro maze I got lost in. I found:
>
> #ifdef CONFIG_TRACE_IRQFLAGS
> DEFINE_EVENT(preemptirq_template, irq_disable,
> TP_PROTO(unsigned long ip, unsigned long parent_ip),
> TP_ARGS(ip, parent_ip));
>
> DEFINE_EVENT(preemptirq_template, irq_enable,
> TP_PROTO(unsigned long ip, unsigned long parent_ip),
> TP_ARGS(ip, parent_ip));
> #else
> #define trace_irq_enable(...)
> #define trace_irq_disable(...)
> #define trace_irq_enable_rcuidle(...)
> #define trace_irq_disable_rcuidle(...)
> #endif
>
> But the DEFINE_EVENT doesn't have the "_rcuidle" part. And that's
> where I got lost in the macro maze. I looked at the gcc asm output,
> and there is, indeed:
DEFINE_EVENT
DECLARE_TRACE
__DECLARE_TRACE
__DECLARE_TRACE_RCU
static inline void trace_##name##_rcuidle(proto)
__DO_TRACE
if (rcuidle)
....
> But I also don't see why this is any different from any other tracepoint.
Indeed. I took a wrong turn at some point in the macro jungle :)
So tracing itself is fine, but then if you have probes or bpf programs
attached to a tracepoint these use rcu_read_lock()/unlock() which is
obviosly wrong in rcuidle context.
Thanks,
tglx
next prev parent reply other threads:[~2020-03-01 18:12 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 22:08 [patch 0/8] x86/entry: Consolidation - Part II Thomas Gleixner
2020-02-25 22:08 ` [patch 1/8] x86/entry/64: Trace irqflags unconditionally on when returing to user space Thomas Gleixner
2020-02-27 19:49 ` Borislav Petkov
2020-02-27 22:45 ` Frederic Weisbecker
2020-02-28 8:58 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 2/8] x86/entry/common: Consolidate syscall entry code Thomas Gleixner
2020-02-27 19:57 ` Borislav Petkov
2020-02-27 22:52 ` Frederic Weisbecker
2020-02-28 8:59 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 3/8] x86/entry/common: Mark syscall entry points notrace/nokprobe Thomas Gleixner
2020-02-27 23:15 ` Frederic Weisbecker
2020-02-28 8:59 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code Thomas Gleixner
2020-02-26 5:43 ` Andy Lutomirski
2020-02-26 8:17 ` Peter Zijlstra
2020-02-26 11:20 ` Andy Lutomirski
2020-02-26 19:51 ` Thomas Gleixner
2020-02-29 14:44 ` Thomas Gleixner
2020-02-29 19:25 ` Andy Lutomirski
2020-02-29 23:58 ` Steven Rostedt
2020-03-01 10:16 ` Thomas Gleixner
2020-03-01 14:37 ` Andy Lutomirski
2020-03-01 15:21 ` Thomas Gleixner
2020-03-01 16:00 ` Andy Lutomirski
2020-03-01 18:12 ` Thomas Gleixner [this message]
2020-03-01 18:26 ` Paul E. McKenney
2020-03-01 18:54 ` Andy Lutomirski
2020-03-01 19:30 ` Paul E. McKenney
2020-03-01 19:39 ` Andy Lutomirski
2020-03-01 20:18 ` Paul E. McKenney
2020-03-02 0:35 ` Steven Rostedt
2020-03-02 6:47 ` Masami Hiramatsu
2020-03-02 1:10 ` Joel Fernandes
2020-03-02 2:18 ` Andy Lutomirski
2020-03-02 2:36 ` Joel Fernandes
2020-03-02 5:40 ` Andy Lutomirski
2020-03-02 8:10 ` Thomas Gleixner
2020-03-01 18:23 ` Steven Rostedt
2020-03-01 18:20 ` Steven Rostedt
2020-02-27 23:11 ` Frederic Weisbecker
2020-02-28 9:00 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 5/8] x86/entry/common: Provide trace/kprobe safe exit to user space functions Thomas Gleixner
2020-02-26 5:45 ` Andy Lutomirski
2020-02-26 8:15 ` Peter Zijlstra
2020-02-27 15:43 ` Alexandre Chartre
2020-02-27 15:53 ` Thomas Gleixner
2020-02-25 22:08 ` [patch 6/8] x86/entry: Move irq tracing to syscall_slow_exit_work Thomas Gleixner
2020-02-26 5:47 ` Andy Lutomirski
2020-02-27 16:12 ` Alexandre Chartre
2020-02-25 22:08 ` [patch 7/8] x86/entry: Move irq tracing to prepare_exit_to_user_mode() Thomas Gleixner
2020-02-26 5:50 ` Andy Lutomirski
2020-02-26 19:53 ` Thomas Gleixner
2020-02-26 20:07 ` Andy Lutomirski
2020-02-25 22:08 ` [patch 8/8] x86/entry: Move irqflags tracing to do_int80_syscall_32() Thomas Gleixner
2020-02-27 16:46 ` Alexandre Chartre
2020-02-28 13:49 ` Thomas Gleixner
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