On Mon, Aug 10, 2026 at 09:26:06AM -0400, Steven Rostedt wrote:
> On Mon, 10 Aug 2026 08:54:22 +0100
> Vincent Donnefort <[email protected]> wrote:
>
> > This is probably the issue.
> >
> > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> > index c2cbdb3ef727..a64cdc925078 100644
> > --- a/kernel/trace/ring_buffer.c
> > +++ b/kernel/trace/ring_buffer.c
> > @@ -3534,7 +3534,7 @@ rb_event_index(struct ring_buffer_per_cpu
> > *cpu_buffer, struct ring_buffer_event
> > {
> > unsigned long addr = (unsigned long)event;
> >
> > - addr &= rb_subbuf_size(cpu_buffer->buffer) - 1;
> > + addr &= (unsigned long)rb_subbuf_size(cpu_buffer->buffer) - 1;
> >
> > return addr - BUF_PAGE_HDR_SIZE;
> > }
> > @@ -4123,7 +4123,7 @@ rb_try_to_discard(struct ring_buffer_per_cpu
> > *cpu_buffer,
> > new_index = rb_event_index(cpu_buffer, event);
> > old_index = new_index + rb_event_ts_length(event);
> > addr = (unsigned long)event;
> > - addr &= ~(rb_subbuf_size(cpu_buffer->buffer) - 1);
> > + addr &= ~((unsigned long)rb_subbuf_size(cpu_buffer->buffer) - 1);
> >
> > bpage = READ_ONCE(cpu_buffer->tail_page);
> >
> > @@ -5033,7 +5033,7 @@ rb_decrement_entry(struct ring_buffer_per_cpu
> > *cpu_buffer,
> > struct buffer_page *bpage = cpu_buffer->commit_page;
> > struct buffer_page *start;
> >
> > - addr &= ~(rb_subbuf_size(cpu_buffer->buffer) - 1);
> > + addr &= ~((unsigned long)rb_subbuf_size(cpu_buffer->buffer) - 1);
>
> What about just making those functions return unsigned long instead of
> having to add typecasts all over. It shouldn't hurt the places it's made an
> int? Although I'm not sure if bots will complain. :-/
I thought about that, but it is used to assign to 32-bits variables, such as
ring_buffer_cpu_meta::subbuf_size or in ring_buffer_subbuf_size_get().
so it felt the (unsigned long) cast wasn't that bad in the end.
Alternatively, I could make all the "size" (_size, _capacity _max_data_size)
related accessors "unsigned long" and do the same for the buffer_data_page and
buffer_page accessors?
And just WARN() if we set one of the meta data fields with more than U32_MAX?
>
> >
> > /* Do the likely case first */
> > if (likely(bpage->page == (void *)addr)) {
> >
> >
> > I will resend a V3 dropping the 3 first patches you have applied already.
>
> Yeah, they are already in Linus's tree.
>
> -- Steve
I have sent the v3:
https://lore.kernel.org/all/[email protected]/
--
Vincent
