From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBB69225403 for ; Wed, 14 Jan 2026 15:09:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768403375; cv=none; b=QTw9fkhPimUXyz+aENR3WdHhhTj42KK06IBIJtIeFu7zEHelaAcUUctXYK4uHzMNle1qW9Xr36cY3Nv25h7EIJEtbpo9gHsTPXaEZ4PWlUp8opFE+MpgMWVHpexicNhKzR5H8EEua1tHpi1fAkyNiMqwu8BVN+otgkgI8M/KOjY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768403375; c=relaxed/simple; bh=NjQcw3R1HG1lqH+BXR/8hfFLHfGLdskGN3ZJqE7vtCU=; h=Message-ID:Date:MIME-Version:From:Subject:To:Content-Type; b=k6VyNG6A0qMBIlB9d/DU/Z6adWiq19bS1ESogNHIDiSJ63W+sBklNXMtZlyrkFuYN3yumxV12R7jm7mQ5z3TK5TM+6Zq6czXddx0cCDDQ/kncN8FFEHAkGt3wc0/ZLg4FTfHXsb458vxKXXKBz682E76ASOKq0OaUePEzP9l7S0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Ecua977+; arc=none smtp.client-ip=91.218.175.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Ecua977+" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1768403370; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=Aj0QrLht9aaTuQ/P2tUQw70XaX1PNaO97a64PoVhs7M=; b=Ecua977+S4zE7pTvHGcXdg6R2bH1vPX6s2W/t55EmuipkpWvJYgBhlwELl2Hi8UD2PMWae LsoRoJStxI7Pkbt2aU0FPWVEYRZV4hW2d0k6tdCKdEb1n9Vo4yWa35wxcQPVMIIjNXFGEp A+NBTAI7B9G2l8/xQBVhYHDTifwPuaU= Date: Wed, 14 Jan 2026 23:09:21 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Tao Chen Subject: The same symbol is printed twice when use tracepoint to get stack To: Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , Jiri Olsa , LKML , bpf Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Hi guys, When using tracepoints to retrieve stack information, I observed that perf_trace_sched_migrate_task was printed twice. And the issue also occurs with tools using libbpf. sudo bpftrace -e ' tracepoint:sched:sched_migrate_task { printf("Task %s migrated by:\n", args->comm); print(kstack); }' Task kcompactd0 migrated by: perf_trace_sched_migrate_task+9 perf_trace_sched_migrate_task+9 set_task_cpu+353 detach_task+77 detach_tasks+281 sched_balance_rq+452 sched_balance_newidle+504 pick_next_task_fair+84 __pick_next_task+66 pick_next_task+43 __schedule+332 schedule+41 schedule_hrtimeout_range+239 do_poll.constprop.0+668 do_sys_poll+499 __x64_sys_ppoll+220 x64_sys_call+5722 do_syscall_64+126 entry_SYSCALL_64_after_hwframe+118 Task jbd2/sda2-8 migrated by: perf_trace_sched_migrate_task+9 perf_trace_sched_migrate_task+9 set_task_cpu+353 try_to_wake_up+365 default_wake_function+26 autoremove_wake_function+18 __wake_up_common+118 __wake_up+55 __jbd2_log_start_commit+195 env: bpftrace v0.21.2 ubuntu24.04，6.14.0-36-generic The issue is as follows: https://github.com/bpftrace/bpftrace/issues/4949 It seems that there is no special handling in the kernel. Does anyone has thoughts on this issue. Thanks. BPF_CALL_4(bpf_get_stack_raw_tp, struct bpf_raw_tracepoint_args *, args, void *, buf, u32, size, u64, flags) { struct pt_regs *regs = get_bpf_raw_tp_regs(); int ret; if (IS_ERR(regs)) return PTR_ERR(regs); perf_fetch_caller_regs(regs); ret = bpf_get_stack((unsigned long) regs, (unsigned long) buf, (unsigned long) size, flags, 0); put_bpf_raw_tp_regs(); return ret; } -- Best Regards Tao Chen