From nobody Sat Jul 25 21:59:35 2026 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (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 624033DDDB1; Mon, 13 Jul 2026 09:37:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783935434; cv=none; b=RgGsbCFlvQlRRKx1Wv+nxe0MCF8K49ZDwyaNYoaovE/H1hpGWJgSW/7+QkI471S3W+2wZn652zSor2oSu9JTKjjxBZzABahhlvAZuqN0mQbzo4AamUqBoGHkrkvziAsHe/pS+++ICpL2R5iyCHUNUWPFPUs8bWeXwxsH2Lks0kU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783935434; c=relaxed/simple; bh=2Yr7RXSaPvo7tOCzezDgY/runQK1vgIe5hy8eLHSdAg=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=KuVOMlfiB5tz9/qSwokMGnltgZoMQacgYTFV54n6cGI4q1I90Fj5Bt8yDfPOM/WjL4Bqy6SgtMyngaCNQ0MxadGYN+9t1pbCR94Q2/fI3UbcfEM3iwpHGM/buTI/+lg1fhMQ6vmZHg1l341P+k6IFzD7h6ubk4+/CnPsIW9GYCw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 63050f5a7e9e11f1aa26b74ffac11d73-20260713 X-CTIC-Tags: HR_CC_COUNT, HR_CC_DOMAIN_COUNT, HR_CC_NAME, HR_CC_NO_NAME, HR_CTE_8B HR_CTT_MISS, HR_DATE_H, HR_DATE_WKD, HR_DATE_ZONE, HR_FROM_NAME HR_SJ_LANG, HR_SJ_LEN, HR_SJ_LETTER, HR_SJ_NOR_SYM, HR_SJ_PHRASE HR_SJ_PHRASE_LEN, HR_SJ_WS, HR_TO_COUNT, HR_TO_DOMAIN_COUNT, HR_TO_NO_NAME IP_TRUSTED, SRC_TRUSTED, DN_TRUSTED, SA_TRUSTED, SA_EXISTED SN_TRUSTED, SN_EXISTED, SPF_NOPASS, DKIM_NOPASS, DMARC_NOPASS CIE_GOOD, CIE_GOOD_SPF, GTI_FG_BS, GTI_RG_INFO, GTI_C_BU AMN_GOOD, ABX_MISS_RDNS X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.12,REQID:737e3777-f411-42a7-bbc1-a3fc128e6dc5,IP:10, URL:0,TC:0,Content:-5,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTIO N:release,TS:5 X-CID-INFO: VERSION:1.3.12,REQID:737e3777-f411-42a7-bbc1-a3fc128e6dc5,IP:10,UR L:0,TC:0,Content:-5,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION: release,TS:5 X-CID-META: VersionHash:e7bac3a,CLOUDID:94c11187df5fd3d362ed3d2b4bdf846f,BulkI D:260713173658XB6UB7LO,BulkQuantity:0,Recheck:0,SF:10|38|66|78|102|127|136 |850|865|898,TC:nil,Content:0|15|50,EDM:-3,IP:-2,URL:0,File:nil,RT:nil,Bul k:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0 ,BRE:0,ARC:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: 63050f5a7e9e11f1aa26b74ffac11d73-20260713 X-User: lihongfu@kylinos.cn Received: from localhost.localdomain [(223.70.159.239)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_256_GCM_SHA384 256/256) with ESMTP id 970018875; Mon, 13 Jul 2026 17:36:55 +0800 From: Hongfu Li To: peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, james.clark@linaro.org Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, hongfu.li@linux.dev, Hongfu Li Subject: [PATCH] perf doc: Fix mmap failure checks in topdown example Date: Mon, 13 Jul 2026 17:36:26 +0800 Message-Id: <20260713093626.492180-1-lihongfu@kylinos.cn> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Use MAP_FAILED instead of NULL to detect mmap errors, and fix the slots_p variable name typo in the sample code. Signed-off-by: Hongfu Li --- tools/perf/Documentation/topdown.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/perf/Documentation/topdown.txt b/tools/perf/Documentatio= n/topdown.txt index 5c17fff694ee..fd4214f9a7b0 100644 --- a/tools/perf/Documentation/topdown.txt +++ b/tools/perf/Documentation/topdown.txt @@ -87,7 +87,7 @@ if (slots_fd < 0) =20 /* Memory mapping the fd permits _rdpmc calls from userspace */ void *slots_p =3D mmap(0, getpagesize(), PROT_READ, MAP_SHARED, slots_fd, = 0); -if (!slot_p) +if (slots_p =3D=3D MAP_FAILED) .... error ... =20 /* @@ -107,7 +107,7 @@ if (metrics_fd < 0) =20 /* Memory mapping the fd permits _rdpmc calls from userspace */ void *metrics_p =3D mmap(0, getpagesize(), PROT_READ, MAP_SHARED, metrics_= fd, 0); -if (!metrics_p) +if (metrics_p =3D=3D MAP_FAILED) ... error ... =20 Note: the file descriptors returned by the perf_event_open calls must be m= emory --=20 2.25.1