On 2021/9/10 下午11:38, Peter Zijlstra wrote: > On Thu, Sep 09, 2021 at 11:13:21AM +0800, 王贇 wrote: >> 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 > > kernel/events/Makefile has: > > ifdef CONFIG_FUNCTION_TRACER > CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE) > endif > > Which, afaict, should avoid the above, no? I'm afraid it's not working for this case, the start point of tracing is at lock_acquire() which is not from 'kernel/events/core', the following PF related function are also not from 'core', prevent ftrace on 'core' can't prevent this from happen... Regards, Michael Wang >
