From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id A30106B0055 for ; Tue, 29 Nov 2011 02:49:59 -0500 (EST) Received: from /spool/local by e6.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 29 Nov 2011 02:49:53 -0500 Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id pAT7nn3c334716 for ; Tue, 29 Nov 2011 02:49:49 -0500 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id pAT7nlUT018065 for ; Tue, 29 Nov 2011 05:49:49 -0200 Date: Tue, 29 Nov 2011 13:18:07 +0530 From: Srikar Dronamraju Subject: Re: [PATCH v7 3.2-rc2 3/30] uprobes: register/unregister probes. Message-ID: <20111129074807.GA13445@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20111118110631.10512.73274.sendpatchset@srdronam.in.ibm.com> <20111118110713.10512.9461.sendpatchset@srdronam.in.ibm.com> <1322494194.2921.147.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1322494194.2921.147.camel@twins> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Linus Torvalds , Oleg Nesterov , Andrew Morton , LKML , Linux-mm , Ingo Molnar , Andi Kleen , Christoph Hellwig , Steven Rostedt , Roland McGrath , Thomas Gleixner , Masami Hiramatsu , Arnaldo Carvalho de Melo , Anton Arapov , Ananth N Mavinakayanahalli , Jim Keniston , Stephen Wilson * Peter Zijlstra [2011-11-28 16:29:54]: > On Fri, 2011-11-18 at 16:37 +0530, Srikar Dronamraju wrote: > > +static void __unregister_uprobe(struct inode *inode, loff_t offset, > > + struct uprobe *uprobe) > > +{ > > + struct list_head try_list; > > + struct address_space *mapping; > > + struct vma_info *vi, *tmpvi; > > + struct vm_area_struct *vma; > > + struct mm_struct *mm; > > + loff_t vaddr; > > + > > + mapping = inode->i_mapping; > > + INIT_LIST_HEAD(&try_list); > > + while ((vi = find_next_vma_info(&try_list, offset, > > + mapping, false)) != NULL) { > > + if (IS_ERR(vi)) > > + break; > > So what kind of half-assed state are we left in if we try an unregister > under memory pressure and how do we deal with that? > Agree, Even I had this concern and wanted to see if there are ways to deal with this. - One approach would be pass extra GFG flags while we do allocations atleast in the unregister_uprobe. Drawback of this approach: if the system is already under memory pressure we shouldnt exert more pressure by asking it to repeat. - The other approach would be to cache these temporary objects while we insert probes. i.e keep these metadata around. I am sure you wouldnt want to add additional metadata. - Third approach would be to have a completion/worker routine kick in if unregister_uprobe fails due to memory allocations. This looks better than the rest. Do you have any other approaches that we could try? -- thanks and regards Srikar -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org