From: Philippe Gerum <rpm@xenomai.org>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Xenomai <xenomai@lists.linux.dev>
Subject: Re: [dovetail-5.10] Re: tracing: irq_pipeline: add pipeline awareness
Date: Fri, 22 Sep 2023 10:18:35 +0200 [thread overview]
Message-ID: <87cyyamx9x.fsf@xenomai.org> (raw)
In-Reply-To: <1eb4952e-f76f-4831-87e1-5effe76700ca@siemens.com>
Jan Kiszka <jan.kiszka@siemens.com> writes:
> Hi Philippe,
>
> what is this fixme in 5.10.y-dovetail-rebase (and only there) about?
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index d3e0ae1168069..8d10bdfd8ccf4 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
>
> ...
>
> @@ -7229,10 +7231,10 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
> break;
> /* Now, we're going to swap */
> if (iter->cpu_file == RING_BUFFER_ALL_CPUS) {
> - local_irq_disable();
> + hard_local_irq_disable();
> update_max_tr(tr, current, smp_processor_id(), NULL);
> - local_irq_enable();
> - } else {
> + hard_local_irq_enable();
> + } else { /* FIXME: irq_pipeline */
> smp_call_function_single(iter->cpu_file, tracing_swap_cpu_buffer,
> (void *)tr, 1);
> }
>
> To my understanding, tracing_snapshot_write() will only be called in-
> band, no?
>
> Jan
Yes, but I'm still pondering the implications of the in-band vs oob
concurrent accesses on the upstream commit #c5d30d6aa as a fix for a SMP
race between buffer swap & write ops. Assuming this is not an issue
eventually, the code would look like this:
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8d10bdfd8ccf4..46cdc6ecf64a9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7168,7 +7168,9 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
static void tracing_swap_cpu_buffer(void *tr)
{
+ hard_local_irq_disable();
update_max_tr_single((struct trace_array *)tr, current, smp_processor_id());
+ hard_local_irq_enable();
}
static ssize_t
@@ -7234,7 +7236,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
hard_local_irq_disable();
update_max_tr(tr, current, smp_processor_id(), NULL);
hard_local_irq_enable();
- } else { /* FIXME: irq_pipeline */
+ } else {
smp_call_function_single(iter->cpu_file, tracing_swap_cpu_buffer,
(void *)tr, 1);
}
--
Philippe.
prev parent reply other threads:[~2023-09-22 8:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 17:38 [dovetail-5.10] Re: tracing: irq_pipeline: add pipeline awareness Jan Kiszka
2023-09-21 17:52 ` Jan Kiszka
2023-09-22 8:18 ` Philippe Gerum [this message]
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