From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (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 184992773CB for ; Thu, 4 Sep 2025 12:18:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.89.141.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756988321; cv=none; b=R9YCSYXiKjz6bM1hV5GWe4y30Tji/XLW5jAMvEkRR5kS8SqzKZzwSBpG4tSh2+pXx6JQvGsOkWPa+IQJRnnQ4z4RPBZh5i0ahCJZ+qevaYI/pAxiaef1Oohv4XOs7qWOF+W8WTOuRHQL70XdvD/Bk/PXzmzeUpoIL+mPDCr2cGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756988321; c=relaxed/simple; bh=O+fmhNDnfriW/CrDMSv1sKFfrH/YMKi23TpuE36ZHf8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mucgmkD0Uiy+d7Kv7WCp8zitKNznKRQUjqQkP8wzipahLkrDqezGILwSGPory7zfXZ/oAlDcKXLenEAQi3HjriFNgp7PHFUfuFtLfmKc1J9C31iqAC8hd3z+z2kr5PuwysvMx7S8WJTmOXWQ802ypnDAx9VY/0ujWv49+4xG6NE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=t82d6lIT; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="t82d6lIT" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uFCLS3pJ8t3bQm1VwY7Wirh9MMSwgQnfRsfmBY+FBQw=; b=t82d6lIT8x0EZVKMNELLws/RG6 1CHbYccEbDb544bfA5Cm3QaXwva8HERMvPey9udDMJbIDh2q2lH9bYyen1PqucP8rZQit3GSUdVzF 9jFlSJJO/9k9c0MkvSmP8dvRNjHCalQBdJsDiAAd4r34xjyK7SuP88W6ITkE1lWaQCsC/kofYeBGi 8Gqp2V9gDIkFYWxpVjgHEloiRh42JTtgAv15rGBzlXFauUbpC6L1bExE5xsflsx//t/dAmeBSJzdg KOOmnCBnJv5+1A3UZRA58lQc/gyimRzGy4YxiGd/e1BXDvQF7Wvzhnj3RwrdDB0WUxlV8CObHB9Ms rP3b9/jA==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uu8vE-00000001E1b-0dKQ; Thu, 04 Sep 2025 12:18:36 +0000 Date: Thu, 4 Sep 2025 13:18:36 +0100 From: Al Viro To: Dave Chinner Cc: Linus Torvalds , linux-fsdevel@vger.kernel.org, Christian Brauner , Jan Kara Subject: Re: [PATCHES v3][RFC][CFT] mount-related stuff Message-ID: <20250904121836.GO39973@ZenIV> References: <20250825044046.GI39973@ZenIV> <20250828230706.GA3340273@ZenIV> <20250903045432.GH39973@ZenIV> <20250903181429.GL39973@ZenIV> <20250904032024.GN39973@ZenIV> <20250904055514.GA3194878@ZenIV> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250904055514.GA3194878@ZenIV> Sender: Al Viro On Thu, Sep 04, 2025 at 06:55:14AM +0100, Al Viro wrote: > Bugger... Either I've got false 'good' at several points, or it's something > brought in by commit 2004cef11ea0 "Merge tag 'sched-core-2024-09-19' of > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip" - bisection has > converged to something within the first 48 commits of the branch in question. > > Which is not impossible, but then the underlying race could've been there > for years before that, only to be exposed by timing changes ;-/ > > Anyway, I'll get the bisection to the end, but it looks like the end result > won't be particularly useful... It's definitely within that branch; breakage reproduce on dae4320b29f0 "sched: Fixup set_next_task() implementations" and does *not* reproduce on 8e2e13ac6122 "sched/fair: Cleanup pick_task_fair() vs throttle" Trying to bisect it further runs into a bisect hazard left there - commit 54a58a787791 "sched/fair: Implement DELAY_ZERO" has +SCHED_FEAT(DELAY_ZERO, true) and 2e0199df252a "sched/fair: Prepare exit/cleanup paths for delayed_dequeue" - + if (sched_feat(DELAY_ZERO) && p->se.vlag > 0) 6 commits before the definition. I'm not going to try and reorder that branch into something bisectable - I do not know that area anywhere near well enough for that. In any case, I doubt that it's a scheduler bug; something exposed by the timings change, but that's about it...