From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) (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 1139419C556; Fri, 11 Jul 2025 03:22:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752204167; cv=none; b=W2hxCC5ijSlrSJQ2TyQFdYQEZqRV05XxZ9W+2dbXCJ//VgzUbZU4DTXxccXfKMdy6FzjCImY+hrDV5VYWL87V5daGoXtQkvhvKjc/xrv2OgNfKIzICXpFlNIEi1xHEUtvfLStkia/FJFgBy/n62OsEfB153zZ0CzbcupzrifrIg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752204167; c=relaxed/simple; bh=AOMERvCwHn+nDByLA1zBfaEarNOSftfY+xvP8R8XKvE=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=fgAQMaJUzSlHVsxz4O80U8Mbmr4mcPxnAQ7afoU3JRFd6vd7n2fpeq8KHxf/DgJPOUmAg37ynDyo9qgP7+Qh2w4wUIoJgv7UYSHopsJ13mAGlUlofyqvXrm8u3Ei3LKIDbbCl6D0/eqT4ONzNUpkeCvaevoGlgthh47CLiMWUWw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 7B89F110CE2; Fri, 11 Jul 2025 03:22:37 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf16.hostedemail.com (Postfix) with ESMTPA id 97CAB2000D; Fri, 11 Jul 2025 03:22:35 +0000 (UTC) Date: Thu, 10 Jul 2025 23:22:34 -0400 From: Steven Rostedt To: Tengda Wu CC: Masami Hiramatsu , Mathieu Desnoyers , Shuah Khan , Yuanhe Shu , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_-next=5D_selftests/ftrace=3A_Prevent_p?= =?US-ASCII?Q?otential_failure_in_subsystem-enable_test_case?= User-Agent: K-9 Mail for Android In-Reply-To: <2bf277fb-a1b8-47f8-9133-e3ca27327eda@huaweicloud.com> References: <20250710130134.591066-1-wutengda@huaweicloud.com> <20250710153409.3135fb17@batman.local.home> <2bf277fb-a1b8-47f8-9133-e3ca27327eda@huaweicloud.com> Message-ID: <17189AF8-34DC-4E5C-9233-ECADAECBBD26@goodmis.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-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 97CAB2000D X-Stat-Signature: rsybpaqecasmewttfb7hque4sw3nmd4c X-Rspamd-Server: rspamout06 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+jeMYjTDi2JaJ5j5GAHF08erVJMS/K1Kk= X-HE-Tag: 1752204155-110836 X-HE-Meta: U2FsdGVkX1+ezatnzjfsETpKVj2ysZSUlftTfPcdsnJymo1vta4pcBVQla7FuSgHwhgzARc7k591EzkdEOdrd5v3DOqh8GuzjDWZAFPF5zQkZenXP073HwCpbJB+gIAWIJmcZ0f7mEkrWfIo6BmYnajgIRsbOirlQ2Bm21r0ZU2thMX8DgtW6l73Xg5MJhBpCR/dRLt5m4Yl4m4ZOQk6fVlvcAcgKXMDkWNiz0lTmE5Ez+lbSL0W+pxvOJDQxLlsg/wowvT7LQx7Gc0bfz8g1F5wtrYrblRFnbxasaH0ij0I23fVHPKJvZmyDMaZUHp5XzuRit+28et/xfnhFCyDh5XQm4N9l6yX+9y+2ea6K4ePw5rh4SyJSD/U5pcBBaPj7NI3YGp26pY= On July 10, 2025 10:48:54 PM EDT, Tengda Wu w= rote: > >The patch works well - after ~50 test iterations, we haven't observed any >recurrence of the test case failures=2E > >However, I'm concerned that using 'cat trace_pipe' (like the original >'cat trace' method) could bring back the stopping problem [1] on slower >systems=2E > >Could a slow trace_pipe reader (slower than sched event generation rate) >reintroduce the original race condition? > Only if it doesn't find three different events, in which case the test wou= ld fail regardless=2E The awk script exits out as soon as it finds 3: unique events=2E It won't = go forever, even on slower machines=2E -- Steve >[1] https://git=2Ekernel=2Eorg/pub/scm/linux/kernel/git/torvalds/linux=2E= git/commit/?id=3D1a4ea83a6e67f1415a1f17c1af5e9c814c882bb5 > >Some test details: > >$ =2E/ftracetest -vvv subsystem-enable=2Etc >[=2E=2E=2E] >+ echo sched:* >+ yield >+ ping 127=2E0=2E0=2E1 -c 1 >PING 127=2E0=2E0=2E1 (127=2E0=2E0=2E1) 56(84) bytes of data=2E >64 bytes from 127=2E0=2E0=2E1: icmp_seq=3D1 ttl=3D64 time=3D0=2E538 ms > >--- 127=2E0=2E0=2E1 ping statistics --- >1 packets transmitted, 1 received, 0% packet loss, time 1ms >rtt min/avg/max/mdev =3D 0=2E538/0=2E538/0=2E538/0=2E000 ms >+ check_unique >+ cat trace_pipe >+ grep -v ^# >+ awk=20 > BEGIN { cnt =3D 0; } > { > for (i =3D 0; i < cnt; i++) { > if (event[i] =3D=3D $5) { > break; > } > } > if (i =3D=3D cnt) { > event[cnt++] =3D $5; > if (cnt > 2) { > exit; > } > } > } > END { > printf "%d", cnt; > } >+ count=3D3 >+ [ 3 -lt 3 ] >+ do_reset >[=2E=2E=2E] > >Regards, >Tengda