From: Daniel Bristot de Oliveira <bristot@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>,
Valentin Schneider <vschneid@redhat.com>
Cc: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org,
loongarch@lists.linux.dev, linux-mips@vger.kernel.org,
openrisc@lists.librecores.org, linux-parisc@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
x86@kernel.org, "Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Russell King <linux@armlinux.org.uk>,
Nicholas Piggin <npiggin@gmail.com>, Guo Ren <guoren@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [RFC PATCH v2 8/8] sched, smp: Trace smp callback causing an IPI
Date: Fri, 18 Nov 2022 17:42:34 +0100 [thread overview]
Message-ID: <1ab5082c-bec5-53f2-501b-f15f7e8edbd9@redhat.com> (raw)
In-Reply-To: <Y3dMiyFn6TG1s5g3@hirez.programming.kicks-ass.net>
On 11/18/22 10:12, Peter Zijlstra wrote:
> On Thu, Nov 17, 2022 at 02:45:29PM +0000, Valentin Schneider wrote:
>
>>> + if (trace_ipi_send_cpumask_enabled()) {
>>> + call_single_data_t *csd;
>>> + smp_call_func_t func;
>>> +
>>> + csd = container_of(node, call_single_data_t, node.llist);
>>> +
>>> + func = sched_ttwu_pending;
>>> + if (CSD_TYPE(csd) != CSD_TYPE_TTWU)
>>> + func = csd->func;
>>> +
>>> + if (raw_smp_call_single_queue(cpu, node))
>>> + trace_ipi_send_cpumask(cpumask_of(cpu), _RET_IP_, func);
>> So I went with the tracepoint being placed *before* the actual IPI gets
>> sent to have a somewhat sane ordering between trace_ipi_send_cpumask() and
>> e.g. trace_call_function_single_entry().
>>
>> Packaging the call_single_queue logic makes the code less horrible, but it
>> does mix up the event ordering...
> Keeps em sharp ;-)
>
Having the trace before the IPI avoids the (non ideal) case where the trace stops because of
an IPI execution before we have trace about who sent it... :-(.
-- Daniel
next prev parent reply other threads:[~2022-11-18 16:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 18:29 [RFC PATCH v2 0/8] Generic IPI sending tracepoint Valentin Schneider
2022-11-02 18:29 ` [RFC PATCH v2 1/8] DO-NOT-MERGE: tracing: Add __cpumask to denote a trace event field that is a cpumask_t Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 2/8] trace: Add trace_ipi_send_cpumask() Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 3/8] sched, smp: Trace IPIs sent via send_call_function_single_ipi() Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 4/8] smp: Trace IPIs sent via arch_send_call_function_ipi_mask() Valentin Schneider
2022-11-17 9:08 ` Peter Zijlstra
2022-11-17 14:23 ` Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 5/8] irq_work: Trace self-IPIs sent via arch_irq_work_raise() Valentin Schneider
2022-11-17 9:10 ` Peter Zijlstra
2022-11-02 18:33 ` [RFC PATCH v2 6/8] treewide: Trace IPIs sent via smp_send_reschedule() Valentin Schneider
2022-11-17 9:12 ` Peter Zijlstra
2022-11-17 14:24 ` Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 7/8] smp: reword smp call IPI comment Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 8/8] sched, smp: Trace smp callback causing an IPI Valentin Schneider
2022-11-17 14:12 ` Peter Zijlstra
2022-11-17 14:45 ` Valentin Schneider
2022-11-18 9:12 ` Peter Zijlstra
2022-11-18 16:42 ` Daniel Bristot de Oliveira [this message]
2022-11-14 17:27 ` [RFC PATCH v2 0/8] Generic IPI sending tracepoint Steven Rostedt
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