From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9B3F0FBF6; Fri, 24 Jan 2025 22:00:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737756048; cv=none; b=fMnJT1+Z/6tDGvvjjidchrRbgvLSBm1U4j1mrSObCxgAmLTUAZomAy2rImNAXF3dw0KR8BIIqxkaAvWS8dEI2XGrIF5ZJ2YHJZZMsRtUGN2aX7Ha30N6D/dXad8Xa+B2DqF7dF6Z2D/jEVGCiqUspcCeMlMYquL3w/9/OcGJE0o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737756048; c=relaxed/simple; bh=ocW0QHrHLA2keOhEunkKkNQ18McRRkljQW5O5h4kBUw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iahg8RuCeS0D0aNpj84DBtwqmqPo3DvJx3q5xy5KVvSI8NU9EFwkE9Gsh3PWt9TfrLxPcSs8ialgC2VKrMTBc2IWhYcLRymGJHjHYV3E5AQ2+X4I5YFH6CBfXBcklfoKkR5Q3QTH0DLN1mlxQWK2g+7s+TBi9qcA/V/enloHnQE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EIrFDrji; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EIrFDrji" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FACCC4CED2; Fri, 24 Jan 2025 22:00:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737756048; bh=ocW0QHrHLA2keOhEunkKkNQ18McRRkljQW5O5h4kBUw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EIrFDrjihPexKBMV6E5FMSG654Graa5cInGnIPWWWpgfyK+pJYDnau0Pd1BT0S2l0 wxCArJy2qMevwjGUJE5IfeR3Ks/5GUPEbO7q4tyaD/OCPwHojTKf27Jz25s8El/buv dZzRSzgrpSl/wophPoZ9UiXhTgsuHjRcxDzgEv2miNBONLbxbmiI0jqPj1wRy1H79b cB2YQo4VJRSbppsG8oB4mu2VAxREWDT4Kop3Bmgs1uGgf2cW2QA5FiUinNz3dDcIKF aC0Bz//Y95KcvAVN8/aXp+j9cdsyusojI8fos40dcQWiGJgv8/aTFIFMstiF126J8s RKwxBDXyStKbw== Date: Fri, 24 Jan 2025 14:00:45 -0800 From: Josh Poimboeuf To: Andrii Nakryiko Cc: x86@kernel.org, Peter Zijlstra , Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Indu Bhagat , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, Mark Brown , linux-toolchains@vger.kernel.org, Jordan Rome , Sam James , linux-trace-kernel@vger.kernel.org, Jens Remus , Mathieu Desnoyers , Florian Weimer , Andy Lutomirski , Masami Hiramatsu , Weinan Liu Subject: Re: [PATCH v4 32/39] perf: Remove get_perf_callchain() 'crosstask' argument Message-ID: <20250124220045.hduc3az4neoutebq@jpoimboe> References: <73229250c0279667f617c3d6da121c6621164e4d.1737511963.git.jpoimboe@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Jan 24, 2025 at 10:13:23AM -0800, Andrii Nakryiko wrote: > On Tue, Jan 21, 2025 at 6:32 PM Josh Poimboeuf wrote: > > @@ -430,10 +429,8 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, > > if (task && user && !user_mode(regs)) > > goto err_fault; > > > > - /* get_perf_callchain does not support crosstask user stack walking > > - * but returns an empty stack instead of NULL. > > - */ > > - if (crosstask && user) { > > + /* get_perf_callchain() does not support crosstask stack walking */ > > + if (crosstask) { > > crosstask stack trace is supported for kernel stack traces (see > get_callchain_entry_for_task() call), so this is breaking that case Oh I see, thanks. BTW, that seems dubious, does it do anything to ensure the task isn't running? Otherwise the unwind is going to be a wild ride. -- Josh