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ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

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Because, ring_buffer_subbuf_order_set() can clear cpu_buffer->free_page,
hold cpu_buffer->lock to prevent races with
ring_buffer_alloc_read_page() and ring_buffer_free_read_page().

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260813131152.3589632-3-vdonnefort@google.com
Fixes: 8e7b58c27b ("ring-buffer: Just update the subbuffers when changing their allocation order")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260810125633.3344684-1-vdonnefort%40google.com # patch 3
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Vincent Donnefort 2026-08-13 14:11:44 +01:00 committed by Steven Rostedt
parent 234b1a72e9
commit 24974bd0da
1 changed files with 2 additions and 0 deletions
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2
kernel/trace/ring_buffer.c
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@ -7431,8 +7431,10 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
cpu_buffer->nr_pages_to_update = 0;
arch_spin_lock(&cpu_buffer->lock);
old_free_data_page = cpu_buffer->free_page;
cpu_buffer->free_page = NULL;
arch_spin_unlock(&cpu_buffer->lock);
rb_head_page_activate(cpu_buffer);