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 5F937181B8D for ; Thu, 8 Aug 2024 14:40:31 +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=1723128032; cv=none; b=qHBWAUWJbV4KXY2eewUlUtHx/oyAO5jSckRnGaKUAiI7X9WTWC/I3E+EcEWUk2rVvbuNa9Y6j776wDB2SlZuf5cMj+Jf8pU00dMA1K+q4yKad8UNxIWFW2yxAwmZ068duwwBBI7bgL4GaYF+Kg2nf/C8w2KtCokGkbvU8URBW7c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723128032; c=relaxed/simple; bh=IAcpC0yUr0S8fp2OMIDVu4XVdUAl5xhCver/7xE68Ic=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZmOdS8W44CQn1D3mBenQcYN/CSLiSq1mkd0lp/b/YOgeGkhdHGwg2lc9yLNT/9q6G1qFVeW5HCYan++usVsnTpij9HE/op+qhOSPRCEnKJwvuYNUIJN2fuvwzmXyY4z/jT+2RMPTLckXBRxrd8/U/qPGC0MNmmnuVBYykGh1xDU= 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=Gkue7WKk; 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="Gkue7WKk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723128030; 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=PygIMfTc4oYFST/M6dQiSfvy+yNiOOgfx4Q/j0leG9Y=; b=Gkue7WKkRZ6wB1/nl9zGFUYHW2OfXqxgCJJMtskAG9FEz1y9SnD8ptsfeQknU4YNOGNZL1 1QiitaF49Z9+JC8+QdbP5B5NdW/JEuBDA/moCshrbjVJbbZdIY0PP5Cx2QmerKbUtG88m1 FnGbe7YqU9rN/gZ+UDAn3zMNuUYuggY= Received: from mx-prod-mc-01.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-110-uSVS_D2lM7iUSJ3UDPmhMw-1; Thu, 08 Aug 2024 10:40:22 -0400 X-MC-Unique: uSVS_D2lM7iUSJ3UDPmhMw-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 36E6619772DA; Thu, 8 Aug 2024 14:40:20 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.189]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 941551956052; Thu, 8 Aug 2024 14:40:16 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 8 Aug 2024 16:40:18 +0200 (CEST) Date: Thu, 8 Aug 2024 16:40:14 +0200 From: Oleg Nesterov To: Andrii Nakryiko Cc: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org Subject: Re: [PATCH v2 4/6] uprobes: travers uprobe's consumer list locklessly under SRCU protection Message-ID: <20240808144013.GG8020@redhat.com> References: <20240808002118.918105-1-andrii@kernel.org> <20240808002118.918105-5-andrii@kernel.org> 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: <20240808002118.918105-5-andrii@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On 08/07, Andrii Nakryiko wrote: > > @@ -1127,18 +1105,30 @@ void uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc) > int err; > > down_write(&uprobe->register_rwsem); > - if (WARN_ON(!consumer_del(uprobe, uc))) { > - err = -ENOENT; > - } else { > - err = register_for_each_vma(uprobe, NULL); > - /* TODO : cant unregister? schedule a worker thread */ > - if (unlikely(err)) > - uprobe_warn(current, "unregister, leaking uprobe"); > - } > + > + list_del_rcu(&uc->cons_node); > + err = register_for_each_vma(uprobe, NULL); > + > up_write(&uprobe->register_rwsem); > > - if (!err) > - put_uprobe(uprobe); > + /* TODO : cant unregister? schedule a worker thread */ > + if (unlikely(err)) { > + uprobe_warn(current, "unregister, leaking uprobe"); > + return; Looks wrong... We can (should) skip put_uprobe(), but we can't avoid synchronize_srcu(). The caller can free the consumer right after return. You even added a fat comment below. Yes, the problem will go away after you split it into nosync/sync, but still. Oleg.