[PATCH v2 2/2] tracing/snapshot: Use work_on_cpu to avoid -EBUSY during snapshot swap
From: Tengda Wu <hidden>
Date: 2026-08-03 00:56:56
Also in:
lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
The snapshot operation currently uses smp_call_function_single() to invoke ring_buffer_swap_cpu() on the target CPU. Since interrupt can hit at any point during the write path, this may return -EBUSY if the target CPU is actively writing to the buffer, which could be confusing to users who may not understand the internal state of the ring buffer. Replace smp_call_function_single() with work_on_cpu() for the snapshot operation. This ensures that the swap only occurs after the ongoing write completes. Signed-off-by: Tengda Wu <redacted> --- kernel/trace/trace_snapshot.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_snapshot.c b/kernel/trace/trace_snapshot.c
index 07b43c9863a2..22323c97289b 100644
--- a/kernel/trace/trace_snapshot.c
+++ b/kernel/trace/trace_snapshot.c@@ -625,9 +625,12 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file) return ret; } -static void tracing_swap_cpu_buffer(void *tr) +static long tracing_swap_cpu_buffer(void *tr) { + local_irq_disable(); update_max_tr_single((struct trace_array *)tr, current, smp_processor_id()); + local_irq_enable(); + return 0; } static ssize_t
@@ -689,8 +692,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt, update_max_tr(tr, current, smp_processor_id(), NULL); local_irq_enable(); } else { - smp_call_function_single(iter->cpu_file, tracing_swap_cpu_buffer, - (void *)tr, 1); + work_on_cpu(iter->cpu_file, tracing_swap_cpu_buffer, (void *)tr); } tracing_disarm_snapshot(tr); break;
--
2.34.1