From: Shaurya Rane <[email protected]> The kernel's lockdep validator detected a circular locking dependency in ring_buffer_map(). The function was acquiring the per-CPU 'cpu_buffer->mapping_lock' before the global 'buffer->mutex'.
This violates the established locking hierarchy where 'buffer->mutex' should be acquired first, leading to a potential deadlock. Fix this by reordering the mutex acquisition to lock 'buffer->mutex' before 'cpu_buffer->mapping_lock', satisfying the lockdep requirements and preventing the deadlock. Reported-by: [email protected] Signed-off-by: Shaurya Rane <[email protected]> --- kernel/trace/ring_buffer.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 43460949ad3f..82c3d5d2dcf6 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -7222,9 +7222,10 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu, if (!cpumask_test_cpu(cpu, buffer->cpumask)) return -EINVAL; - + cpu_buffer = buffer->buffers[cpu]; - + + guard(mutex)(&buffer->mutex); guard(mutex)(&cpu_buffer->mapping_lock); if (cpu_buffer->user_mapped) { -- 2.34.1
