On Wed, Oct 14, 2026 at 05:51:26PM -0400, Steven Rostedt wrote:
> On Tue, 13 Oct 2026 11:20:46 +0100
> Vincent Donnefort <[email protected]> wrote:
>
> > Persistent and remote buffer memory is pre-allocated by the time
> > __rb_allocate_pages() is called. Skip si_mem_available() to avoid
> > wrongly failing the allocation under memory pressure.
> >
> > For the same reason, unset user_thread.
> >
> > Fixes: be68d63a139b ("ring-buffer: Add ring_buffer_alloc_range()")
> > Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes")
> > Signed-off-by: Vincent Donnefort <[email protected]>
> > ---
> > kernel/trace/ring_buffer.c | 41 +++++++++++++++++++-------------------
> > 1 file changed, 21 insertions(+), 20 deletions(-)
> >
> > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> > index 04bb94c29f58..b3a30a0413a5 100644
> > --- a/kernel/trace/ring_buffer.c
> > +++ b/kernel/trace/ring_buffer.c
> > @@ -2442,20 +2442,30 @@ static int __rb_allocate_pages(struct
> > ring_buffer_per_cpu *cpu_buffer,
> > struct trace_buffer *buffer = cpu_buffer->buffer;
> > struct ring_buffer_cpu_meta *meta = NULL;
> > struct buffer_page *bpage, *tmp;
> > - bool user_thread = current->mm != NULL;
> > struct ring_buffer_desc *desc = NULL;
> > + bool user_thread = false;
> > long i;
> >
> > - /*
> > - * Check if the available memory is there first.
> > - * Note, si_mem_available() only gives us a rough estimate of available
> > - * memory. It may not be accurate. But we don't care, we just want
> > - * to prevent doing any allocation when it is obvious that it is
> > - * not going to succeed.
> > - */
> > - i = si_mem_available();
> > - if (i < nr_pages)
> > - return -ENOMEM;
> > + if (buffer->range_addr_start) {
> > + meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
> > + } else if (buffer->remote) {
> > + desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu);
> > + if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1)))
> > + return -EINVAL;
> > + } else {
> > + /*
> > + * Check if the available memory is there first.
> > + * Note, si_mem_available() only gives us a rough estimate of
> > available
> > + * memory. It may not be accurate. But we don't care, we just
> > want
> > + * to prevent doing any allocation when it is obvious that it is
> > + * not going to succeed.
> > + */
> > + i = si_mem_available();
> > + if (i < nr_pages)
> > + return -ENOMEM;
> > +
> > + user_thread = current->mm != NULL;
>
> Not caused by this patch but we need to update this to:
>
> user_thread = is_user_task(current);
>
> I may add that.
I can send a v3 if that helps.
--
Vincent
>
> -- Steve
>
> > + }
> >
> > /*
> > * If a user thread allocates too much, and si_mem_available()
> > @@ -2469,15 +2479,6 @@ static int __rb_allocate_pages(struct
> > ring_buffer_per_cpu *cpu_buffer,
> > if (user_thread)
> > set_current_oom_origin();
> >
> > - if (buffer->range_addr_start)
> > - meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
> > -
> > - if (buffer->remote) {
> > - desc = ring_buffer_desc(buffer->remote->desc, cpu_buffer->cpu);
> > - if (!desc || WARN_ON(desc->nr_page_va != (nr_pages + 1)))
> > - return -EINVAL;
> > - }
> > -
> > for (i = 0; i < nr_pages; i++) {
> >
> > bpage = alloc_cpu_page(cpu_buffer->cpu);
>
