From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 D163983CA0 for ; Wed, 31 Jan 2024 14:13:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706710406; cv=none; b=czhv8Ca/EnXDrGTAMpZp+o0ulyFWto+plGkxyE5T80J6oLsxOzBIUJ9rK9wK0oarUt/MwuQKRCjQMI6fQ/yZ3ODx9EcAfgxkopmBKUESX2d3ZkuGsETmJUd0M6cdbogJU4CGOmAx3vbdSjbIRQz9lp4jad6Fnj9vC+WPS1nBerk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706710406; c=relaxed/simple; bh=SSgcJTAtCezKBIlSDqex7c15iUz3dD6SPXbEzwWDyYs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HrJGLwXMtZmGkhT/ld1Ja4ClMZRiIniYxdXh4IwHzuwYsWZuJwSWxm/DhwQSR4CQTdlAFlQGi5RknSdOCID8jeDCEPj3pG3hJJ+8MYBZfu7yX/d1BPRYrSrpwuDgUmrSIeCarQz15040acalCSfx0MQClRBL+j38s4jmCkzTXHA= 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=c57hcCXE; arc=none smtp.client-ip=170.10.133.124 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="c57hcCXE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706710404; 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=E6N7rRVRfH9o+RQBIxOXu8QZ0PlRxq4vDv7nz6/O5wk=; b=c57hcCXEZQLTWc4Eub9DyRpgILQ2zQXQVqsNLke3PktV9te48NgcWDVw6rPQO8sw691UQY qBgKn1s1yKCdnb4TI+kKrAqbCHJkQDrfOKifGsoLyNXnOVH6IacB+MMpdJBuO+cne8QV8x xFNvsOn8dAHjWyor01rH+TkWxQ9nmQ0= 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-394-7TeHyjMQNrOVJm7QSFuhZA-1; Wed, 31 Jan 2024 09:13:22 -0500 X-MC-Unique: 7TeHyjMQNrOVJm7QSFuhZA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (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 6848185A59A; Wed, 31 Jan 2024 14:13:21 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.249]) by smtp.corp.redhat.com (Postfix) with SMTP id 2C5313C2E; Wed, 31 Jan 2024 14:13:19 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 31 Jan 2024 15:12:06 +0100 (CET) Date: Wed, 31 Jan 2024 15:12:04 +0100 From: Oleg Nesterov To: Christian Brauner Cc: "Eric W. Biederman" , Tycho Andersen , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/1] pidfd: implement PIDFD_THREAD flag for pidfd_open() Message-ID: <20240131141204.GA24130@redhat.com> References: <20240131132541.GA23632@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20240131132541.GA23632@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Before I forget this... After this patch we can easily add another feature, pidfd_poll() can add, say, POLLHUP to poll_flags if the pid is "dead". So the user can do poll(pidfd, { .revents = POLLHUP }); and it will block until release_task() is called and this pid is no longer in use (pid_task() == NULL). Do you think this can be useful? Oleg.