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Re: [RFC] [PATCH 2.6.37-rc5-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree.
- From: Peter Zijlstra <peterz at infradead dot org>
- To: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Christoph Hellwig <hch at infradead dot org>, Andi Kleen <andi at firstfloor dot org>, Oleg Nesterov <oleg at redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>, SystemTap <systemtap at sources dot redhat dot com>, Linux-mm <linux-mm at vger dot kernel dot org>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Frederic Weisbecker <fweisbec at gmail dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Andrew Morton <akpm at linux-foundation dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Tue, 25 Jan 2011 13:15:40 +0100
- Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree.
- References: <20101216095714.23751.52601.sendpatchset@localhost6.localdomain6> <20101216095803.23751.41491.sendpatchset@localhost6.localdomain6>
On Thu, 2010-12-16 at 15:28 +0530, Srikar Dronamraju wrote:
> +static int match_inode(struct uprobe *uprobe, struct inode *inode,
> + struct rb_node **p)
> +{
> + struct rb_node *n = *p;
> +
> + if (inode < uprobe->inode)
> + *p = n->rb_left;
> + else if (inode > uprobe->inode)
> + *p = n->rb_right;
> + else
> + return 1;
> + return 0;
> +}
> +
> +static int match_offset(struct uprobe *uprobe, unsigned long offset,
> + struct rb_node **p)
> +{
> + struct rb_node *n = *p;
> +
> + if (offset < uprobe->offset)
> + *p = n->rb_left;
> + else if (offset > uprobe->offset)
> + *p = n->rb_right;
> + else
> + return 1;
> + return 0;
> +}
> +
> +/*
> + * Find a uprobe corresponding to a given inode:offset
> + * Acquires treelock
> + */
> +static struct uprobe *find_uprobe(struct inode * inode,
> + unsigned long offset)
> +{
> + struct rb_node *n = uprobes_tree.rb_node;
> + struct uprobe *uprobe, *u = NULL;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&treelock, flags);
> + while (n) {
> + uprobe = rb_entry(n, struct uprobe, rb_node);
> +
> + if (match_inode(uprobe, inode, &n)) {
> + if (match_offset(uprobe, offset, &n)) {
> + if (atomic_inc_not_zero(&uprobe->ref))
> + u = uprobe;
> + break;
> + }
> + }
> + }
> + spin_unlock_irqrestore(&treelock, flags);
> + return u;
> +}
> +
> +/*
> + * Check if a uprobe is already inserted;
> + * If it does; return refcount incremented uprobe
> + * else add the current uprobe and return NULL
> + * Acquires treelock.
> + */
> +static struct uprobe *insert_uprobe_rb_node(struct uprobe *uprobe)
> +{
> + struct rb_node **p = &uprobes_tree.rb_node;
> + struct rb_node *parent = NULL;
> + struct uprobe *u;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&treelock, flags);
> + while (*p) {
> + parent = *p;
> + u = rb_entry(parent, struct uprobe, rb_node);
> + if (u->inode > uprobe->inode)
> + p = &(*p)->rb_left;
> + else if (u->inode < uprobe->inode)
> + p = &(*p)->rb_right;
> + else {
> + if (u->offset > uprobe->offset)
> + p = &(*p)->rb_left;
> + else if (u->offset < uprobe->offset)
> + p = &(*p)->rb_right;
> + else {
> + atomic_inc(&u->ref);
If the lookup can find a 'dead' entry, then why can't we here?
> + goto unlock_return;
> + }
> + }
> + }
> + u = NULL;
> + rb_link_node(&uprobe->rb_node, parent, p);
> + rb_insert_color(&uprobe->rb_node, &uprobes_tree);
> + atomic_set(&uprobe->ref, 2);
> +
> +unlock_return:
> + spin_unlock_irqrestore(&treelock, flags);
> + return u;
> +}
It would be nice if you could merge the find and 'acquire' thing, the
lookup is basically the same in both cases.
Also, I'm not quite sure on the name of that last function, its not a
strict insert and what's the trailing _rb_node about? That lookup isn't
called find_uprobe_rb_node() either is it?