From 9fd830120fd61ab934aff90361586e65b8dd020d Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Wed, 16 Sep 2026 16:28:12 +0100 Subject: ring-buffer: Clean up resize_disabled checks ring_buffer_subbuf_order_set() checks for resize_disabled twice under the same buffer->mutex hold. Moreover, this check duplicates the logic in ring_buffer_resize(). Create a common helper rb_resize_disabled() to factor out this code. Link: https://patch.msgid.link/20260916152813.105082-2-vdonnefort@google.com Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 63 +++++++++++++++++++++------------------------- 1 file changed, 28 insertions(+), 35 deletions(-) (limited to 'kernel/trace') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 1b148cd891c8..15e3b9938e0f 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3282,6 +3282,21 @@ static void update_pages_handler(struct work_struct *work) complete(&cpu_buffer->update_done); } +static bool rb_resize_disabled(struct trace_buffer *buffer, int cpu) +{ + lockdep_assert_held(&buffer->mutex); + + if (cpu != RING_BUFFER_ALL_CPUS) + return atomic_read(&buffer->buffers[cpu]->resize_disabled); + + for_each_buffer_cpu(buffer, cpu) { + if (atomic_read(&buffer->buffers[cpu]->resize_disabled)) + return true; + } + + return false; +} + /** * ring_buffer_resize - resize the ring buffer * @buffer: the buffer to resize. @@ -3322,20 +3337,17 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, nr_pages = rb_calculate_nr_pages(buffer, size); - if (cpu_id == RING_BUFFER_ALL_CPUS) { - /* - * Don't succeed if resizing is disabled, as a reader might be - * manipulating the ring buffer and is expecting a sane state while - * this is true. - */ - for_each_buffer_cpu(buffer, cpu) { - cpu_buffer = buffer->buffers[cpu]; - if (atomic_read(&cpu_buffer->resize_disabled)) { - err = -EBUSY; - goto out_err_unlock; - } - } + /* + * Don't succeed if resizing is disabled, as a reader might be + * manipulating the ring buffer and is expecting a sane state while + * this is true. + */ + if (rb_resize_disabled(buffer, cpu_id)) { + err = -EBUSY; + goto out_err_unlock; + } + if (cpu_id == RING_BUFFER_ALL_CPUS) { /* calculate the pages to update */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; @@ -3407,16 +3419,6 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, if (nr_pages == cpu_buffer->nr_pages) goto out; - /* - * Don't succeed if resizing is disabled, as a reader might be - * manipulating the ring buffer and is expecting a sane state while - * this is true. - */ - if (atomic_read(&cpu_buffer->resize_disabled)) { - err = -EBUSY; - goto out_err_unlock; - } - cpu_buffer->nr_pages_to_update = nr_pages - cpu_buffer->nr_pages; @@ -7471,13 +7473,9 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) old_capacity = rb_subbuf_capacity(buffer); - /* The mmap fast path reads subbuf_order without buffer->mutex. */ - for_each_buffer_cpu(buffer, cpu) { - if (!cpumask_test_cpu(cpu, buffer->cpumask)) - continue; - if (atomic_read(&buffer->buffers[cpu]->resize_disabled)) - return -EBUSY; - } + /* Check it is resizable before we touch subbuf_order */ + if (rb_resize_disabled(buffer, RING_BUFFER_ALL_CPUS)) + return -EBUSY; atomic_inc(&buffer->record_disabled); @@ -7494,11 +7492,6 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order) cpu_buffer = buffer->buffers[cpu]; - if (atomic_read(&cpu_buffer->resize_disabled)) { - err = -EBUSY; - goto error; - } - /* Update the number of pages to match the new size */ nr_pages = rb_calculate_nr_pages(buffer, old_capacity * buffer->buffers[cpu]->nr_pages); -- cgit v1.2.3