From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 82E9D16F265; Fri, 11 Jul 2025 03:37:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752205044; cv=none; b=ZyB5q53hOHmoz4AjiTMFV1pR7SQHL6E+kyNSPh6ajTzRruZoYV3sCynu6EUjhYXQ1wp1U85EcV2e8CMZWxsw8qbK3k5nABP2s47+UQXXQOJ8CWXjkDe1HCRh6j2qIYt1iW+lvP9vp/Zslm81MdIalCAGr6wRYGuvZXaIciQz0QU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752205044; c=relaxed/simple; bh=Due+ZsEVsVqHWbezajRnc6wVUa4NOCwIiPko78BclaM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OfXpzFNZYG47QeVHnkHxJ2gUhCvUGF7rqu/Ge+6UyzldP6CU/GLy2VC8dRTY5SRl8dh5FXdeJjL+Er/l8WIerBjfqEb9VP0EqKhAobJHN27+TnwKmJixRxT2KxBSOMIjvbrYPvnJ9cqXx7qw4vaZNV4V04AAEbSI7uOrJmsNr8U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=none smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4bdcpl0sr4zYQtt8; Fri, 11 Jul 2025 11:37:19 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id E4BC11A18F3; Fri, 11 Jul 2025 11:37:17 +0800 (CST) Received: from [10.67.110.36] (unknown [10.67.110.36]) by APP1 (Coremail) with SMTP id cCh0CgBHDTLqhnBokcFWBQ--.9098S2; Fri, 11 Jul 2025 11:37:15 +0800 (CST) Message-ID: <6fc6cf98-516a-4121-b593-57bc4f7f36cf@huaweicloud.com> Date: Fri, 11 Jul 2025 11:37:14 +0800 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next] selftests/ftrace: Prevent potential failure in subsystem-enable test case To: Steven Rostedt 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 References: <20250710130134.591066-1-wutengda@huaweicloud.com> <20250710153409.3135fb17@batman.local.home> <2bf277fb-a1b8-47f8-9133-e3ca27327eda@huaweicloud.com> <17189AF8-34DC-4E5C-9233-ECADAECBBD26@goodmis.org> Content-Language: en-US From: Tengda Wu In-Reply-To: <17189AF8-34DC-4E5C-9233-ECADAECBBD26@goodmis.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:cCh0CgBHDTLqhnBokcFWBQ--.9098S2 X-Coremail-Antispam: 1UD129KBjvJXoW7tr47Ar13uF18JFW8Jry7ZFb_yoW8Ar4rpa y7JFnxKF4kAr4ft3Z2gw4DAryUtrWktryUCws8tw1ruFs0vw13tFyUArWUuFZrZF4Du3y2 vwn0q3ZF9ryq9aDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUymb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxV AFwI0_GcCE3s1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2 j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7x kEbVWUJVW8JwACjcxG0xvEwIxGrwCY1x0262kKe7AKxVWUAVWUtwCF04k20xvY0x0EwIxG rwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4 vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IY x2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr0_Gr1lIxAIcVCF04k26c xKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAF wI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07UK2NtUUUUU= X-CM-SenderInfo: pzxwv0hjgdqx5xdzvxpfor3voofrz/ On 2025/7/11 11:22, Steven Rostedt wrote: > > > On July 10, 2025 10:48:54 PM EDT, Tengda Wu wrote: >> > >> The patch works well - after ~50 test iterations, we haven't observed any >> recurrence of the test case failures. >> >> 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. >> >> 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 would fail regardless. > > The awk script exits out as soon as it finds 3: unique events. It won't go forever, even on slower machines. > > -- Steve Got it, thank you for explaining this. I have no further questions. -- Tengda > >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1a4ea83a6e67f1415a1f17c1af5e9c814c882bb5 >> >> Some test details: >> >> $ ./ftracetest -vvv subsystem-enable.tc >> [...] >> + echo sched:* >> + yield >> + ping 127.0.0.1 -c 1 >> PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data. >> 64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.538 ms >> >> --- 127.0.0.1 ping statistics --- >> 1 packets transmitted, 1 received, 0% packet loss, time 1ms >> rtt min/avg/max/mdev = 0.538/0.538/0.538/0.000 ms >> + check_unique >> + cat trace_pipe >> + grep -v ^# >> + awk >> BEGIN { cnt = 0; } >> { >> for (i = 0; i < cnt; i++) { >> if (event[i] == $5) { >> break; >> } >> } >> if (i == cnt) { >> event[cnt++] = $5; >> if (cnt > 2) { >> exit; >> } >> } >> } >> END { >> printf "%d", cnt; >> } >> + count=3 >> + [ 3 -lt 3 ] >> + do_reset >> [...] >> >> Regards, >> Tengda