From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793942274; b=3AUSLQGsTsZ2ELuKk9u6g8NSr41CsgFg7ZkKjCNt84p7Rc6PLS2kOrAKqSUnZT824s05 iDk9k2Ug5KCCWNRtPBKb23ZUCuytnzVZPj3Vflb1fo/UML+uu6zTOtqy4eglUm86LY2Wa wlUXQvWoUOnMay91t/mkPMxXtDAVvzLo2L2a91pIcUsrlU3XEDWifF+6S4FztTxhAwLY2 J0mr2tTZWt0fJMQlPamDorcDGZFqamCnE5G5JIVtdBEQZQWS4AvqLvMJSo7Cfm+VIaKw+ 9GQAaTKxyWIJ8w11kcuh8UIJJsZ6QttLzUalB2fmQllJmlqR/OY9vcILkHeO6k3MX5A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793942274; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=NFSJ9NYhYA4NX2x2SYS23L83g95j7y9yh/pYjXP3o4s=; b=yYcVn1buWcz5mCZrCNpfdCMBuh47zyjRvf2HLM1PmU1Wy64E7hKFXx8x/L/n95O4CznJ 7rtzQbK4XHLG/1CZpmsxlNk1slFCrccTQbPxSkb6Eks6QTqbYp3rM6aoYDBP9ceVQV7Zy i9kxGEaeIJhLsBxgIS5kY5cFH7D0kv5Y92x4NKceyH0/XOEa3mrcohcl48HXvAJZGd3GS X4gimWiANQecoI6sFc10wgevCJR+pQEd9Xem5QiKuNShMdiu80a6mohwnutxSZc3L+Knk uKr8sPPKyCZu2XFrlFZt5m9hIDepoeta3B4hbQh0Fez5gUxx0cyightlMhIqSl9Rvjg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=H4Zppj5k; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6E388606A31B for ; Fri, 6 Nov 2026 05:17:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=H4Zppj5k Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF9A71F0089F; Fri, 6 Nov 2026 05:17:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793942274; bh=NFSJ9NYhYA4NX2x2SYS23L83g95j7y9yh/pYjXP3o4s=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=H4Zppj5kM89uZtt2KFqXM9AGP33Lvr2GSNg/Kn6n9wTPbuB+3r7Gw+pxZGSa7F++r kramcyTgvJTjvSfUd9xZdP3qbHuIAVupCMC0QWPWzi85tWvUVwLUCb8dlflDFgl/wr X4xTgsy0PcDcxXsHImMUobno/WlC7iLsNSpHBxgOKbELQZV+LZhtXNtKUJz6884AU1 7tvrWqBfsZb04GlG/MMiXpeScgMtvtvtHvxgb/m+2/fr42XiQol3N/NrSXWSlArS+L xrbomWdb9umdcQGL+Ico6phd6PUMdyVuHoHOHQuIC95it4+bvV0Q7qee95YLKNmKjA 0h2z9N6Z3s7rA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [Patch v6 20/20] perf/core: Don't overwrite shared LBR stack depth Reply-To: sashiko-reviews@lists.linux.dev To: "Dapeng Mi" Cc: linux-perf-users@vger.kernel.org In-Reply-To: <20261106043257.842864-21-dapeng1.mi@linux.intel.com> References: <20261106043257.842864-1-dapeng1.mi@linux.intel.com> <20261106043257.842864-21-dapeng1.mi@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 06 Nov 2026 05:17:53 +0000 X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > perf_sample_save_brstack() currently clamps the shared LBR stack depth > to min(event->attr.sample_max_stack, brs->nr). This is unsafe because > the global LBR stack is shared across all LBR events, and a small > sample_max_stack from one event can shrink the depth for all others in > the same PMI. >=20 > As a result, later events may output a shorter LBR stack than requested > even when they do not require a small sample depth. Do not overwrite the > shared LBR stack depth in perf_sample_save_brstack(); instead, keep the > per-event limit in a local variable so each event is constrained > independently without mutating global state. >=20 > Reported-by: Sashiko > Fixes: c53e14f1ea4a ("perf: Extend per event callchain limit to branch st= ack") > Signed-off-by: Dapeng Mi Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261106043257.8428= 64-1-dapeng1.mi@linux.intel.com?part=3D20