Re: [PATCH v9 1/2] ring-buffer: Introducing ring-buffer mapping functions
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2023-12-21 17:50:22
Also in:
lkml
On Thu, 21 Dec 2023 17:35:22 +0000 Vincent Donnefort [off-list ref] wrote:
quoted hunk ↗ jump to hunk
@@ -739,6 +747,22 @@ static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int f return (dirty * 100) > (full * nr_pages); } +static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer) +{ + if (unlikely(READ_ONCE(cpu_buffer->mapped))) { + /* Ensure the meta_page is ready */ + smp_rmb(); + WRITE_ONCE(cpu_buffer->meta_page->entries, + local_read(&cpu_buffer->entries)); + WRITE_ONCE(cpu_buffer->meta_page->overrun, + local_read(&cpu_buffer->overrun)); + WRITE_ONCE(cpu_buffer->meta_page->subbufs_touched, + local_read(&cpu_buffer->pages_touched)); + WRITE_ONCE(cpu_buffer->meta_page->subbufs_lost, + local_read(&cpu_buffer->pages_lost)); + } +} + /* * rb_wake_up_waiters - wake up tasks waiting for ring buffer input *@@ -749,6 +773,18 @@ static void rb_wake_up_waiters(struct irq_work *work) { struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); + if (rbwork->is_cpu_buffer) { + struct ring_buffer_per_cpu *cpu_buffer; + + cpu_buffer = container_of(rbwork, struct ring_buffer_per_cpu, + irq_work); + /* + * If the waiter is a cpu_buffer, this might be due to a + * userspace mapping. Let's update the meta-page. + */ + rb_update_meta_page(cpu_buffer); + } + wake_up_all(&rbwork->waiters); if (rbwork->full_waiters_pending || rbwork->wakeup_full) { rbwork->wakeup_full = false;
I think this code would be cleaner if we did:
static void rb_update_meta_page(strucrt rb_irq_work *rbwork)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!rbwork->is_cpu_buffer)
return;
/*
* If the waiter is a cpu_buffer, this might be due to a
* userspace mapping. Let's update the meta-page.
*/
cpu_buffer = container_of(rbwork, struct ring_buffer_per_cpu,
irq_work);
if (unlikely(READ_ONCE(cpu_buffer->mapped))) {
// I don't think we need the "unlikely"
/* Ensure the meta_page is ready */
smp_rmb();
WRITE_ONCE(cpu_buffer->meta_page->entries,
local_read(&cpu_buffer->entries));
WRITE_ONCE(cpu_buffer->meta_page->overrun,
local_read(&cpu_buffer->overrun));
WRITE_ONCE(cpu_buffer->meta_page->subbufs_touched,
local_read(&cpu_buffer->pages_touched));
WRITE_ONCE(cpu_buffer->meta_page->subbufs_lost,
local_read(&cpu_buffer->pages_lost));
}
}
/*
* rb_wake_up_waiters - wake up tasks waiting for ring buffer input
*
* Schedules a delayed work to wake up any task that is blocked on the
* ring buffer waiters queue.
*/
static void rb_wake_up_waiters(struct irq_work *work)
{
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
rb_update_meta_page(cpu_buffer);
wake_up_all(&rbwork->waiters);
if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
rbwork->wakeup_full = false;
rbwork->full_waiters_pending = false;
wake_up_all(&rbwork->full_waiters);
}
}
-- Steve