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 01B4C1A0AF4 for ; Tue, 27 Aug 2024 14:26:26 +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=1724768788; cv=none; b=qHePCmSP/2O7DYqIHQBaZUgAS/QnfUbiYehkedf4SIra/NgEMfegRVMtX2f7qRR103runP9ug2lza1fKHIpoDBrDZy6NiylCTYkPNj7pkrrpyGnAuqmxV+OoOiQRn+by/VSoMbYBSKM98ciA+eVehcxkcXy5wPW4Nj6+jhwRnXc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724768788; c=relaxed/simple; bh=1KqMCRhRHDTcWOdf302AjkxFH5FSKKGXlvdrIrFvszw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WOaAu8i5eoQ+bgUvELpDePObJ2anFewZdlWAniVV4f2bNXTqQuc28IrnTdGVejWWl4Ft493NKeeqUfxc+rRC0bspAqC3K6BbLiwRcEdNpq2CpO/6XeYrNDcnx5hG8cfBhKe7vadmYveEvZhFHELxdkimjphEoVl6bRiNZfeoukw= 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=Dq/jL9C3; 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="Dq/jL9C3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1724768786; 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=ATk3FZ1Fa0HUkud8qmHhRhX+USrye2F9BZBXsUYQl2s=; b=Dq/jL9C39J4xh+yDYy/iQfc7QGWeWiOhk4HRYllCrijlJC3UKQVTpWHnfA22bFpkgnVAjV CYf1YORhms51zub29Jammdj1fwHkCyf8+gc6RwU5rOlI7odOm9xuq5Sdu4OpKWhJaFSDGK t3eEP95QZ5P+XwXWvlQTCv1hIbhCV7A= 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-297-228AWLEJMoe-8sS1s5gzZQ-1; Tue, 27 Aug 2024 10:26:22 -0400 X-MC-Unique: 228AWLEJMoe-8sS1s5gzZQ-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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 45E6B1954B34; Tue, 27 Aug 2024 14:26:20 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.12]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 0A3FC19560AA; Tue, 27 Aug 2024 14:26:15 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 27 Aug 2024 16:26:13 +0200 (CEST) Date: Tue, 27 Aug 2024 16:26:08 +0200 From: Oleg Nesterov To: Jiri Olsa Cc: Tianyi Liu , andrii.nakryiko@gmail.com, mhiramat@kernel.org, ajor@meta.com, albancrequy@linux.microsoft.com, bpf@vger.kernel.org, flaniel@linux.microsoft.com, linux-trace-kernel@vger.kernel.org, linux@jordanrome.com, mathieu.desnoyers@efficios.com Subject: Re: [PATCH v2] tracing/uprobe: Add missing PID filter for uretprobe Message-ID: <20240827142607.GF30765@redhat.com> References: <20240825171417.GB3906@redhat.com> <20240825224018.GD3906@redhat.com> <20240826115752.GA21268@redhat.com> <20240827104052.GD30765@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=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On 08/27, Jiri Olsa wrote: > > On Tue, Aug 27, 2024 at 12:40:52PM +0200, Oleg Nesterov wrote: > > static bool > > uprobe_multi_link_filter(struct uprobe_consumer *con, struct mm_struct *mm) > > { > > struct bpf_uprobe *uprobe; > > + struct task_struct *task, *t; > > + bool ret = false; > > > > uprobe = container_of(con, struct bpf_uprobe, consumer); > > - return uprobe->link->task->mm == mm; > > + task = uprobe->link->task; > > + > > + rcu_read_lock(); > > + for_each_thread(task, t) { > > + struct mm_struct *mm = READ_ONCE(t->mm); > > + if (mm) { > > + ret = t->mm == mm; > > + break; > > + } > > + } > > + rcu_read_unlock(); > > that seems expensive if there's many threads many threads with ->mm == NULL? In the likely case for_each_thread() stops after the first t->mm check. > could we check the leader first and only if it's gone fallback to this? up to you.. Oleg.