Messages in this thread Patch in this message | | | From | 王贇 <> | Subject | [RFC PATCH] perf: fix panic by mark recursion inside perf_log_throttle | Date | Thu, 9 Sep 2021 11:13:21 +0800 |
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When running with ftrace function enabled, we observed panic as below:
traps: PANIC: double fault, error_code: 0x0 [snip] RIP: 0010:perf_swevent_get_recursion_context+0x0/0x70 [snip] Call Trace: <NMI> perf_trace_buf_alloc+0x26/0xd0 perf_ftrace_function_call+0x18f/0x2e0 kernelmode_fixup_or_oops+0x5/0x120 __bad_area_nosemaphore+0x1b8/0x280 do_user_addr_fault+0x410/0x920 exc_page_fault+0x92/0x300 asm_exc_page_fault+0x1e/0x30 RIP: 0010:__get_user_nocheck_8+0x6/0x13 perf_callchain_user+0x266/0x2f0 get_perf_callchain+0x194/0x210 perf_callchain+0xa3/0xc0 perf_prepare_sample+0xa5/0xa60 perf_event_output_forward+0x7b/0x1b0 __perf_event_overflow+0x67/0x120 perf_swevent_overflow+0xcb/0x110 perf_swevent_event+0xb0/0xf0 perf_tp_event+0x292/0x410 perf_trace_run_bpf_submit+0x87/0xc0 perf_trace_lock_acquire+0x12b/0x170 lock_acquire+0x1bf/0x2e0 perf_output_begin+0x70/0x4b0 perf_log_throttle+0xe2/0x1a0 perf_event_nmi_handler+0x30/0x50 nmi_handle+0xba/0x2a0 default_do_nmi+0x45/0xf0 exc_nmi+0x155/0x170 end_repeat_nmi+0x16/0x55
According to the trace we know the story is like this, the NMI triggered perf IRQ throttling and call perf_log_throttle(), which triggered the swevent overflow, and the overflow process do perf_callchain_user() which triggered a user PF, and the PF process triggered perf ftrace which finally lead into a suspected stack overflow.
This patch marking the context as recursion during perf_log_throttle() , so no more swevent during the process and no more panic.
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com> --- kernel/events/core.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 744e872..6063443 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8716,6 +8716,7 @@ static void perf_log_throttle(struct perf_event *event, int enable) struct perf_output_handle handle; struct perf_sample_data sample; int ret; + int rctx;
struct { struct perf_event_header header; @@ -8738,14 +8739,17 @@ static void perf_log_throttle(struct perf_event *event, int enable)
perf_event_header__init_id(&throttle_event.header, &sample, event);
+ rctx = perf_swevent_get_recursion_context(); ret = perf_output_begin(&handle, &sample, event, throttle_event.header.size); - if (ret) - return; + if (!ret) { + perf_output_put(&handle, throttle_event); + perf_event__output_id_sample(event, &handle, &sample); + perf_output_end(&handle); + }
- perf_output_put(&handle, throttle_event); - perf_event__output_id_sample(event, &handle, &sample); - perf_output_end(&handle); + if (rctx >= 0) + perf_swevent_put_recursion_context(rctx); }
/* -- 1.8.3.1
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