From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5DAEA259C80; Fri, 21 Aug 2026 13:00:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787317229; cv=none; b=PNIXbSeMA1IkE0uoL5/NITrt9EIZMdl1wl4SFPA9WjhTUiBeN5n2XGYxav/FnAEOjvepakGXQF6lj7+kg86Tjdwc7QJMH0XIm7mr9NZKpKTWqnFcMTmSpIkMCOPWC4ShEVaNAVo7kVW/2uDtVfYL89fL2BL9H7IRxT8SAQDgyU8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787317229; c=relaxed/simple; bh=4or0CbwZUdsRICugoxoIB+iMkNMtFh+wmgg4sKdKlYM=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=bmjfGnym3pyQSZX4n3jz+r4Z2Pxuoy2dLFqvupCwpU0dFJW7GvQhz5J2784HX6+/KT8f/yLI8TZSGJdCIoDzd1J958kqFzyXSroukm1TIRHYynsoEZjPuovKM+f6SkMOmR56OYxUNxDKB+3SCYifnBZAPpIUon7KV3sOU2NnFRk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QPZqVSDK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QPZqVSDK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A106C1F000E9; Fri, 21 Aug 2026 13:00:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787317228; bh=c6iQ/In1wiUPG7q6JZeCUrEPCWRDwwu9W90dTmMq50g=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=QPZqVSDKzPyrzuce5n/eYwwYfqiO43S9sQEiOqeeq4lX+pdplFwfurKKdtRGIqj7J vi0v/ruwaNWMyOBvuhHmbHVOZXwZpbta73/p0j/5uZfpQl00iGqEpXAPvSbS41I2/8 G8ydMaBW5e9O/1egBRFRwjnr/hNtruF7qdsxPyWCE38jdxuUGaUiKmcAPqdO8Z2HjZ LJYA6Jj68Buolj9flHRv/XmKGTMjsEQdDp/KtdqwYrX8eeNtyByKmgfOCtHwCyMpW1 kCWvu8/amB+eXKHtLQmdL84iG3IhXKysfzW/l1yU0q4JKfSty+ull3uyIiNHX8j/0C BLKI4KbItFXdA== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2] perf evsel: Improve callchain warning for s390 Reply-To: sashiko-reviews@lists.linux.dev To: "Jens Remus" Cc: "Alexander Gordeev" , "Vasily Gorbik" , "Heiko Carstens" , linux-s390@vger.kernel.org, linux-perf-users@vger.kernel.org, "Christian Borntraeger" In-Reply-To: <20260821125538.3721169-1-jremus@linux.ibm.com> References: <20260821125538.3721169-1-jremus@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 21 Aug 2026 13:00:27 +0000 Message-Id: <20260821130027.A106C1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > On s390 the kernel uses s390 back chain instead of frame pointers for > stack tracing of user space since v6.7 commit aa44433ac4ee ("s390: add > USER_STACKTRACE support"). This is because frame pointers on s390 > cannot be used for stack tracing. [1] >=20 > This requires user space to maintain a s390 back chain. For instance > user space to be built with compiler option '-mbackchain' (instead of > '-fno-omit-frame-pointer' used on other architectures, which should > better not be used on s390 [1]). Only few distributions and users build > user space with '-mbackchain'. Therefore '--call-graph fp' may in > practice not produce the expected results. >=20 > Commit ca76fb67ebdd ("perf evlist: Improve default event for s390") > changed the default '-g' option to 'dwarf' on s390 and added a warning > for s390 that wrongly claimed that "Framepointer unwinding lacks kernel > [ ... ] > [1]: s390: Stack tracing using Frame Pointer, Back Chain, and SFrame, > https://conf.gnu-tools-cauldron.org/opo25/talk/Y3CVHY/ >=20 > Fixes: ca76fb67ebdd ("perf evlist: Improve default event for s390") > Signed-off-by: Jens Remus Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260821125538.3721= 169-1-jremus@linux.ibm.com?part=3D1