From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 B362123ED6F; Fri, 11 Jul 2025 12:21:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752236488; cv=none; b=G5tkLWXerBn19aPivs7twzK2psMU+DltdQrEZpR06BvLTd+BmpE5X1rbdOIWz6Ic35gRKuqOUHbEUcUrB2+LD+zegA6w2s/275n8LJX2xXTGRxu6xFw+ZUNqIBmHtKYf3H3M8oXNIdxQ4Can1FmfvIwYr9jT0KaofiR6Rar3KqI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752236488; c=relaxed/simple; bh=hiGIhRKiTOmNcvBHyDkXssmWtLPbnb5hDySW7wqiltI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GsmlEemhGg/0ulvITzEZvRywhGhta3xIVfHTsH+teyRn4s68UJSANzcyIZOFCuEo1eldiI+1NXmfXq4pBeD1L5CE16g4JQPFwQ982T+MWRxRpXQUIwhkO/DWuIP46pOR83Nis8SFXzzeTaxu5Qtc9ehMhJiXzjV5GejJaAzh5go= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=sGKV+wBO; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=rKv0b5SH; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="sGKV+wBO"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="rKv0b5SH" Date: Fri, 11 Jul 2025 14:21:23 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1752236484; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=on+h7+JPsOaseXxmTBL9Mtf7ti/qneEhfl3yBpXQJ5s=; b=sGKV+wBOwX9Xv6F+6+3W4ePgkqqryfMap4ENuXI1zvkYOtof8knG2RqcR8lXsVKDWWPL0a jBnuNXqXROX22aAtbqLjIr5lEIYQeHvjnPS4lQoZ0iP4Nx2KIvCHj0SIgljsA8xrgFaPk3 N/suyvtvIGiF8OmICs4J4uJrK5U51Y4jwZllgoS8RKGU1oj6Rj17AiHCJZ+6rvbO7D23ja 7I89Yi3Ff9Z/0fYooupiIg0DH9Bqo7bnCpddKgQz3RHWGCR2VzfiC0w2gZpzjvlXHdlxad P+dB2pGjSY2YxJKD7pKoQrrlggtnPjVUSPMesoXT7fJyfYgQPFd3n37UjIIcyw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1752236484; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=on+h7+JPsOaseXxmTBL9Mtf7ti/qneEhfl3yBpXQJ5s=; b=rKv0b5SH3ytvcxYzwPp4wxZ980VhtFdQ/LC6EeAhwsLGrooaOYaEvJa0vKVnOV42UHDOgl FG0olKwBw8wsYLCQ== From: Nam Cao To: Xi Ruoyao Cc: Christian Brauner , Frederic Weisbecker , Valentin Schneider , Alexander Viro , Jan Kara , Sebastian Andrzej Siewior , John Ogness , Clark Williams , Steven Rostedt , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-rt-users@vger.kernel.org, Joe Damato , Martin Karsten , Jens Axboe Subject: Re: [PATCH v3] eventpoll: Fix priority inversion problem Message-ID: <20250711122123.qXVK-EkF@linutronix.de> References: <6f99476daa23858dc0536ca182038c8e80be53a2.camel@xry111.site> <20250710062127.QnaeZ8c7@linutronix.de> <20250710083236.V8WA6EFF@linutronix.de> <20250711050217.OMtx7Cz6@linutronix.de> <20250711-ermangelung-darmentleerung-394cebde2708@brauner> <6856a981f0505233726af0301a1fb1331acdce1c.camel@xry111.site> <20250711095830.048P551B@linutronix.de> <7a50fd8af9d21aade901fe4d32e14e698378c82f.camel@xry111.site> 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: <7a50fd8af9d21aade901fe4d32e14e698378c82f.camel@xry111.site> On Fri, Jul 11, 2025 at 08:09:12PM +0800, Xi Ruoyao wrote: > On Fri, 2025-07-11 at 11:58 +0200, Nam Cao wrote: > > On Fri, Jul 11, 2025 at 05:48:56PM +0800, Xi Ruoyao wrote: > > > Sadly, still no luck. > > > > That's unfortunate. > > > > I'm still unable to reproduce the issue, so all I can do is staring at the > > code and guessing. But I'm out of idea for now. > > Same as I. I tried to reproduce in a VM running Fedora Rawhide but > failed. > > > This one is going to be hard to figure out.. > > And I'm afraid this may be a bug in my userspace... Yeah I expect the same thing. In the log you sent me, there are some strange-looking event masks that look like a userspace bug. I tried those strange looking event masks, but epoll_ctl() correctly rejects them with EINVAL. So those masks probably aren't the reason, but they still suggest that userspace may also be broken somewhere else and triggers hard-to-reproduce problems in kernel's epoll. > Then I'd feel guilty if this is reverted because of an invalid bug report > from I :(. But even when userspace is broken, if the kernel patch makes userspace non-functional, I would still call it a kernel bug. So it's a valid bug report alright, don't worry about it. Until we know exactly the root cause, I think revert is the right thing to do. Best regards, Nam