From: Steven Rostedt <rostedt@goodmis.org>
To: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Phil Auld <pauld@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Kate Carcia <kcarcia@redhat.com>,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Clark Willaims <williams@redhat.com>,
John Kacur <jkacur@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V4 05/12] trace/hwlat: Support hotplug operations
Date: Fri, 18 Jun 2021 12:45:03 -0400 [thread overview]
Message-ID: <20210618124503.388fe4d4@oasis.local.home> (raw)
In-Reply-To: <8899f8a8bec38bc600f7a2c61bc6ca664aa7beeb.1623746916.git.bristot@redhat.com>
On Tue, 15 Jun 2021 11:28:44 +0200
Daniel Bristot de Oliveira <bristot@redhat.com> wrote:
> Enable and disable hwlat thread during cpu hotplug online
> and offline operations, respectivelly.
>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
> Cc: Clark Willaims <williams@redhat.com>
> Cc: John Kacur <jkacur@redhat.com>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
> ---
> kernel/trace/trace.c | 6 ++++++
> kernel/trace/trace_hwlat.c | 34 ++++++++++++++++++++++++++++++++++
> 2 files changed, 40 insertions(+)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 9299057feb56..c094865e2f71 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5064,7 +5064,13 @@ int tracing_set_cpumask(struct trace_array *tr,
> arch_spin_unlock(&tr->max_lock);
> local_irq_enable();
>
> + /*
> + * tracing_cpumask is read by tracers that support CPU
> + * hotplug.
> + */
> + get_online_cpus();
> cpumask_copy(tr->tracing_cpumask, tracing_cpumask_new);
> + put_online_cpus();
>
> return 0;
> }
> diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> index 6c6918e86087..9fcfd588c4f6 100644
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -490,6 +490,35 @@ static int start_cpu_kthread(unsigned int cpu)
> return 0;
> }
>
> +/*
> + * hwlat_cpu_init - CPU hotplug online callback function
> + */
> +static int hwlat_cpu_init(unsigned int cpu)
> +{
> + struct trace_array *tr = hwlat_trace;
> +
You need to take the trace_types_lock here, between testing the
hwlat_busy and starting the threads. Otherwise, between the two, the
hwlat tracer could be turned off while a CPU is coming on line, and
then you just started a per cpu thread, while the hwlat tracer is not
enabled.
> + if (!hwlat_busy)
> + return 0;
> +
> + if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
> + return 0;
> +
> + return start_cpu_kthread(cpu);
> +}
> +
> +/*
> + * hwlat_cpu_die - CPU hotplug offline callback function
> + */
> +static int hwlat_cpu_die(unsigned int cpu)
> +{
Same here.
-- Steve
> + if (!hwlat_busy)
> + return 0;
> +
> + stop_cpu_kthread(cpu);
> +
> + return 0;
> +}
> +
> /*
> * start_per_cpu_kthreads - Kick off the hardware latency sampling/detector kthreads
> *
> @@ -903,6 +932,11 @@ __init static int init_hwlat_tracer(void)
> if (ret)
> return ret;
>
> + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/hwlat:online",
> + hwlat_cpu_init, hwlat_cpu_die);
> + if (ret < 0)
> + pr_warn(BANNER "Error to init cpu hotplug support\n");
> +
> init_tracefs();
>
> return 0;
next prev parent reply other threads:[~2021-06-18 16:45 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-15 9:28 [PATCH V4 00/12] hwlat improvements and osnoise/timerlat tracers Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 01/12] trace/hwlat: Fix Clark's email Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 02/12] trace/hwlat: Implement the mode config option Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 03/12] trace/hwlat: Switch disable_migrate to mode none Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 04/12] trace/hwlat: Implement the per-cpu mode Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 05/12] trace/hwlat: Support hotplug operations Daniel Bristot de Oliveira
2021-06-18 16:45 ` Steven Rostedt [this message]
2021-06-18 19:00 ` Steven Rostedt
2021-06-21 11:34 ` Daniel Bristot de Oliveira
2021-06-21 15:25 ` Steven Rostedt
2021-06-21 16:14 ` Daniel Bristot de Oliveira
2021-06-21 17:46 ` Steven Rostedt
2021-06-22 14:05 ` Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 06/12] trace: Add a generic function to read/write u64 values from tracefs Daniel Bristot de Oliveira
2021-06-18 16:56 ` Steven Rostedt
2021-06-21 11:50 ` Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 07/12] trace/hwlat: Use trace_min_max_param for width and window params Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 08/12] trace/hwlat: Remove printk from sampling loop Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 09/12] trace: Add __print_ns_to_secs() and __print_ns_without_secs() helpers Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 10/12] trace: Add osnoise tracer Daniel Bristot de Oliveira
2021-06-18 17:55 ` Steven Rostedt
2021-06-21 12:09 ` Daniel Bristot de Oliveira
2021-06-18 18:27 ` Steven Rostedt
2021-06-21 12:09 ` Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 11/12] trace: Add timerlat tracer Daniel Bristot de Oliveira
2021-06-15 9:28 ` [PATCH V4 12/12] trace/osnoise: Support hotplug operations Daniel Bristot de Oliveira
2021-06-18 19:04 ` Steven Rostedt
2021-06-21 12:18 ` Daniel Bristot de Oliveira
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