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 7E4CF1BFDE7 for ; Fri, 30 Aug 2024 20:21:17 +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=1725049279; cv=none; b=IcipNeQYvoEPbP1rqAd9FoQ2Dtu6Aq2av865D+8gccPd89HfbvxKs4t8mprG2/rLOR2OsYRdJmfWMu8U+x9ivPLJ6zy5BmHJticbjHvjwqZZUMq0oxXmQkzO/8kX/L1meklo3zZoO4bGbU/zAvAtkOvwSct0+tcXYOe5hth7WTc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725049279; c=relaxed/simple; bh=tlG9Z3SWZS45Au6orXQjCifgDXL/6bzfSjTyzN+bf2c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ju2I9nFk0IhwZQKD8g2fQ35h3QLV84DEf9IBWbpGAKj6ejbmyldwjl7p9BLh0RSVuns4hKiPooGRvmGOROv/pL6nHiGyWCjiurm4HUvyZNK04OL8jVgc8ZQ0hXAWEMhY7asdx0GLzFTgTcW3kGnSkt9jI8fJCHucu77m0XpP2p8= 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=hzLxFntC; 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="hzLxFntC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1725049276; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tlG9Z3SWZS45Au6orXQjCifgDXL/6bzfSjTyzN+bf2c=; b=hzLxFntCDVGrHAZ6s+tZassPKMXDCsrgRpqbT/Li0PptNwcUqAZ4R3b4rlwjTB8oy097dA jVVLBzpVPcAt7/SnnTIR3C+IzRS6472Wb/COWOQlEWmQisrrDsPnCmlEwmLTa70xvNq15w zvSmB9xpRRDw1OuXkFidFbIh0ohmPsM= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-54-H6sJ7imwP5qkwnjaTwy5Iw-1; Fri, 30 Aug 2024 16:21:08 -0400 X-MC-Unique: H6sJ7imwP5qkwnjaTwy5Iw-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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 mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DA2AB19560A6; Fri, 30 Aug 2024 20:21:05 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.148]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 02C8119560A3; Fri, 30 Aug 2024 20:20:59 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 30 Aug 2024 22:20:57 +0200 (CEST) Date: Fri, 30 Aug 2024 22:20:50 +0200 From: Oleg Nesterov To: Andrii Nakryiko Cc: Jiri Olsa , Andrii Nakryiko , linux-trace-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH v4 4/8] uprobes: travers uprobe's consumer list locklessly under SRCU protection Message-ID: <20240830202050.GA7440@redhat.com> References: <20240829183741.3331213-1-andrii@kernel.org> <20240829183741.3331213-5-andrii@kernel.org> <20240830143151.GC20163@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 On 08/30, Andrii Nakryiko wrote: > Andrii, let me reply to your email "out of order". First of all: > Can we please let me land these patches first? It's been a while. I > don't think anything is really broken with the logic. OK, agreed. I'll probably write another email (too late for me today), but I agree that "avoid register_rwsem in handler_chain" is obviously a good goal, lets discuss the possible cleanups or even fixlets later, when this series is already applied. > On Fri, Aug 30, 2024 at 7:33 AM Oleg Nesterov wrote: > > > > No, I think you found a problem. UPROBE_HANDLER_REMOVE can be lost if > > uc->filter == NULL of if it returns true. See another reply I sent a > > minute ago. > > > > For better or worse, but I think there is (or has to be) and implicit > contract that if uprobe (or uretprobe for that matter as well, but > that's a separate issue) handler can return UPROBE_HANDLER_REMOVE, > then it *has to* also provide filter. IOW, uc->handler and uc->filter must be consistent. But the current API doesn't require this contract, so this patch adds a difference which I didn't notice when I reviewed this change. (In fact I noticed the difference, but I thought that it should be fine). > If it doesn't provide filter > callback, it doesn't care about PID filtering and thus can't and > shouldn't cause unregistration. At first glance I disagree, but see above. > > I think the fix is simple, plus we need to cleanup this logic anyway, > > I'll try to send some code on Monday. Damn I am stupid. Nothing new ;) The "simple" fix I had in mind can't work. But we can do other things which we can discuss later. Oleg.