From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 6307C64CCC for ; Tue, 20 Feb 2024 09:04:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708419863; cv=none; b=jqG8XfoHl/yafBTqsbJANlwIw0t03H/FfkDT3F62JNKQoJNRfdHVKwo9UhjYPiWtnuLLFVNHYki4xeskDcwUnZCQGkAsU0yGx/GKrdnKKZxX+4GIh+zYFZOSWAh/drkLqpwxK77g8e2B2gHZzvGEw3EJN8+2ibxpSpqsC+MIOQE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708419863; c=relaxed/simple; bh=inr5XQBJ4gP+HBs5eVHAxHMefhyOxnWbYqKIi1snm08=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mK4p1SpWeNbs56ZsPg5zaCjVK4TEj5hy8XOcggSNuy0z2BFCMvAOZqOW39uBgdJRWRhPsQgQ2TYCH62FQ7Rq1/jt/smx9qIzxwYCjk1LzFdnxOGxKKiybvAsZdRZSaSKNiWXZSo+xtkfyii//s52kQibVuUaVTysnWEy/7ir/38= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=b97B3c17; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="b97B3c17" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708419861; 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=inr5XQBJ4gP+HBs5eVHAxHMefhyOxnWbYqKIi1snm08=; b=b97B3c17BPi3b/I9pwGr1IZ6NfPQfvNS4aVt+MY/lgEW2JHo86WGSCN/9iAyQ4UL8pGy6g 8VPoraEnNOA2UaXD4/BMwcp+ialXw/KuQRxDJ2QkJ8q0iQxL0Eiid6IkQXwTkB0M5uoTw+ 5owRePbm8WAuv/dUdFkrPA9f355gfAU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-17-F3ZS-YIEN_6VNDKVyB9QWQ-1; Tue, 20 Feb 2024 04:04:17 -0500 X-MC-Unique: F3ZS-YIEN_6VNDKVyB9QWQ-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 246D085A58E; Tue, 20 Feb 2024 09:04:17 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.160]) by smtp.corp.redhat.com (Postfix) with SMTP id 7BD33492BCC; Tue, 20 Feb 2024 09:04:15 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 20 Feb 2024 10:02:58 +0100 (CET) Date: Tue, 20 Feb 2024 10:02:56 +0100 From: Oleg Nesterov To: Christian Brauner Cc: Andy Lutomirski , "Eric W. Biederman" , Tycho Andersen , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD Message-ID: <20240220090255.GA7783@redhat.com> References: <20240210-dackel-getan-619c70fefa62@brauner> <20240210131518.GC27557@redhat.com> <20240210-chihuahua-hinzog-3945b6abd44a@brauner> <20240210165133.GD27557@redhat.com> <20240214123655.GB16265@redhat.com> <20240216-albern-aufwiegen-1de327c7dafd@brauner> <20240216130625.GA8723@redhat.com> <20240216-ohnedies-improvisieren-58edcc102b6a@brauner> <20240216181214.GA10393@redhat.com> <20240220-einwurf-depesche-d8682be0370c@brauner> Precedence: bulk X-Mailing-List: linux-api@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: <20240220-einwurf-depesche-d8682be0370c@brauner> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 On 02/20, Christian Brauner wrote: > > On Fri, Feb 16, 2024 at 07:12:14PM +0100, Oleg Nesterov wrote: > > On 02/16, Christian Brauner wrote: > > > > > > > SI_USER means that the target can trust the values of si_pid/si_uid > > > > in siginfo. > > > > > > Bah, what an annoying nonsense. I see that this can be used to emulate > > > stuff like SI_TIMER and SI_ASYNCIO. But I very much doubt the value of > > > e.g., emulating SI_DETHREAD. Maybe I'm missing something very obvious. > > > > I don't understand... > > My question was what the purpose of being able to to set si_code to > e.g., SI_DETHREAD is and then to send a signal to yourself? Because it > looks like that's what rt_{tg}sigqueueinfo() and pidfd_send_signal() > allows the caller to do. I'm just trying to understand use-cases for > this. Ah. IIRC criu uses this hack to restore the pending (arbitrary) signals collected at dump time. I was a bit surprise sys_pidfd_send_signal() allows this hack too, I don't think that criu uses pidfd at restore time, but I do not know. Oleg.