From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id 58F52900194 for ; Thu, 23 Jun 2011 22:15:57 -0400 (EDT) Received: from d03relay05.boulder.ibm.com (d03relay05.boulder.ibm.com [9.17.195.107]) by e37.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p5O2CoV9023093 for ; Thu, 23 Jun 2011 20:12:50 -0600 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay05.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5O2Fm8g326816 for ; Thu, 23 Jun 2011 20:15:48 -0600 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5NKFjf5028577 for ; Thu, 23 Jun 2011 14:15:48 -0600 Date: Fri, 24 Jun 2011 07:36:59 +0530 From: Srikar Dronamraju Subject: Re: [PATCH v4 3.0-rc2-tip 7/22] 7: uprobes: mmap and fork hooks. Message-ID: <20110624020659.GA24776@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20110616032645.GF4952@linux.vnet.ibm.com> <1308225626.13240.34.camel@twins> <20110616130012.GL4952@linux.vnet.ibm.com> <1308248588.13240.267.camel@twins> <20110617045000.GM4952@linux.vnet.ibm.com> <1308297836.13240.380.camel@twins> <20110617090504.GN4952@linux.vnet.ibm.com> <1308303665.2355.11.camel@twins> <1308662243.26237.144.camel@twins> <20110622143906.GF16471@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20110622143906.GF16471@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Ingo Molnar , Steven Rostedt , Linux-mm , Arnaldo Carvalho de Melo , Linus Torvalds , Andi Kleen , Hugh Dickins , Christoph Hellwig , Jonathan Corbet , Thomas Gleixner , Masami Hiramatsu , Oleg Nesterov , LKML , Jim Keniston , Roland McGrath , Ananth N Mavinakayanahalli , Andrew Morton > > so I am thinking of a solution that includes most of your ideas along > with using i_mmap_mutex in mmap_uprobe path. > Addressing Peter's comments given on irc wrt i_mmap_mutex. /* Changes: 1. Uses inode->i_mutex instead of uprobes_mutex. 2. Now along with vma rma walk, i_mmap_mutex is even held when we do deletion of uprobes into RB tree. 3. mmap_uprobe takes i_mmap_mutex. Advantages: 1. No need to drop mmap_sem. 2. Now register/unregister can run in parallel. 3. */ void _unregister_uprobe(...) { if (!del_consumer(...)) { // includes tree removal on last consumer return; } if (uprobe->consumers) return; mutex_lock(&mapping->i_mmap_mutex); //sync with mmap. vma_prio_tree_foreach() { // create list } mutex_unlock(&mapping->i_mmap_mutex); list_for_each_entry_safe() { // remove from list down_read(&mm->mmap_sem); remove_breakpoint(); // unconditional, if it wasn't there up_read(&mm->mmap_sem); } mutex_lock(&mapping->i_mmap_mutex); delete_uprobe(uprobe); mutex_unlock(&mapping->i_mmap_mutex); inode->uprobes_count--; mutex_unlock(&inode->i_mutex); } int register_uprobe(...) { uprobe = alloc_uprobe(...); // find or insert in tree mutex_lock(&inode->i_mutex); // sync with register/unregister if (uprobe->consumers) { add_consumer(); goto put_unlock; } add_consumer(); inode->uprobes_count++; mutex_lock(&mapping->i_mmap_mutex); //sync with mmap. vma_prio_tree_foreach(..) { // get mm ref, add to list blah blah } mutex_unlock(&mapping->i_mmap_mutex); list_for_each_entry_safe() { if (ret) { // del from list etc.. // continue; } down_read(mm->mmap_sem); ret = install_breakpoint(); up_read(..); // del from list etc.. // if (ret && (ret == -ESRCH || ret == -EEXIST)) ret = 0; } if (ret) _unregister_uprobe(); put_unlock: mutex_unlock(&inode->i_mutex); put_uprobe(uprobe); return ret; } void unregister_uprobe(...) { mutex_lock(&inode->i_mutex); // sync with register/unregister uprobe = find_uprobe(); // ref++ _unregister_uprobe(); mutex_unlock(&inode->i_mutex); put_uprobe(uprobe); } int mmap_uprobe(struct vm_area_struct *vma) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct mm_struct *mm; struct inode *inode; int ret = 0; if (!valid_vma(vma)) return ret; /* Bail-out */ mm = vma->vm_mm; inode = vma->vm_file->f_mapping->host; if (inode->uprobes_count) return ret; __iget(inode); INIT_LIST_HEAD(&tmp_list); mutex_lock(&mapping->i_mmap_mutex); add_to_temp_list(vma, inode, &tmp_list); list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) { loff_t vaddr; list_del(&uprobe->pending_list); if (ret) continue; vaddr = vma->vm_start + uprobe->offset; vaddr -= vma->vm_pgoff << PAGE_SHIFT; ret = install_breakpoint(mm, uprobe, vaddr); if (ret && (ret == -ESRCH || ret == -EEXIST)) ret = 0; } mutex_unlock(&mapping->i_mmap_mutex); iput(inode); return ret; } int munmap_uprobe(struct vm_area_struct *vma) { struct list_head tmp_list; struct uprobe *uprobe, *u; struct mm_struct *mm; struct inode *inode; int ret = 0; if (!valid_vma(vma)) return ret; /* Bail-out */ mm = vma->vm_mm; inode = vma->vm_file->f_mapping->host; if (inode->uprobes_count) return ret; // walk thro RB tree and decrement mm->uprobes_count walk_rbtree_and_dec_uprobes_count(); //hold treelock. return ret; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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