From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (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 4FFA729A2 for ; Thu, 15 Jan 2026 02:19:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768443575; cv=none; b=nQP4VkCS8sExlx7Krp9kH4/OJx4ckuVoBPfE1h5U56Yy/Y6ny8ZI61ca+8Ft43/Z2j+/2Q2TPS0rFoL+sHNoe0GsFcHDez6y6IKXYLSYKl8JIZFAEkamIlxNPHC0RPIrbhDclg/Vk3XJQ5bVAmb/K0E+mDB6bvVu3KkenN+w1sQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768443575; c=relaxed/simple; bh=2+woLfAOr82Zu4vEfSDri7rx/uLY2IvKY9gx9tjJbBg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eAIWRjojbEF3GxgwcoAAIESB12QuYRoMk3AsVLOW6GSscsfPnucWI6OgxyeEEAgmGR67JyN0u//steIuFdQV62SWBVP9o8B02htr684FMf3Evd/YiVg1Mi5XDYmCqkUxlEKGNF6GHogW1RIvGlaNnSwf7OXSidaYntXuJ/pdKeg= 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=mmvpT/fI; arc=none smtp.client-ip=91.218.175.186 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="mmvpT/fI" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1768443571; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bHRp8SFnQHpQZrbKCWKPuTC6cJKjVHvwHQJMSVyOfLQ=; b=mmvpT/fIiau0YrjLBEdsCdVt+suzyY/H1UEwBV4vTXlkwO/w75tiMcX0e/dBXnH3n4tAnT TbGfhrBY2DlE3TxecYYSHkTZuob2qjiJu/lb+sSpKBynKhZKeemeSMevxUs2q9uV47gy1U UmS/+6hG2QcJsY45Hzxnou1ER2Uaf7g= Date: Thu, 15 Jan 2026 10:18:46 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: The same symbol is printed twice when use tracepoint to get stack To: Jiri Olsa , Alan Maguire Cc: Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , LKML , bpf References: <31e5d219-07f4-46c0-bef1-53af20d473f1@oracle.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Tao Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 在 2026/1/15 05:06, Jiri Olsa 写道: > On Wed, Jan 14, 2026 at 05:35:45PM +0000, Alan Maguire wrote: >> On 14/01/2026 15:09, Tao Chen wrote: >>> 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. >>> >> >> You may need the fix Jiri provided for x86_64 [1]. Eugene mentioned that >> the issue persists for arm64 however [2]. > > yep, there's also follow patchset up for kprobe multi [1] > > jirka > > > [1] https://lore.kernel.org/bpf/20260112214940.1222115-1-jolsa@kernel.org/ > >> >> Alan >> >> [1] https://lore.kernel.org/bpf/20251104215405.168643-2-jolsa@kernel.org/ >> [2] https://lore.kernel.org/all/a38fed68-67bc-98ce-8e12-743342121ae3@oracle.com/ >> >>> 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; >>> } >>> >> Alan, Jiri Thanks for your reply, i see. -- Best Regards Tao Chen