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SubjectRe: [PATCH 2/3] uprobes: Introduce uprobe_is_active()
* Oleg Nesterov <oleg@redhat.com> [2012-11-25 23:33:47]:

> The lifetime of uprobe->rb_node and uprobe->inode is not refcounted,
> delete_uprobe() is called when we detect that uprobe has no consumers,
> and it would be deadly wrong to do this twice.
>
> Change delete_uprobe() to WARN() if it was already called. We use
> RB_CLEAR_NODE() to mark uprobe "inactive", then RB_EMPTY_NODE() can
> be used to detect this case.
>
> RB_EMPTY_NODE() is not used directly, we add the trivial helper for
> the next change.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> kernel/events/uprobes.c | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 53dc2eb..2886c82 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -669,6 +669,10 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad
> return set_orig_insn(&uprobe->arch, mm, vaddr);
> }
>
> +static inline bool uprobe_is_active(struct uprobe *uprobe)
> +{
> + return !RB_EMPTY_NODE(&uprobe->rb_node);
> +}
> /*
> * There could be threads that have already hit the breakpoint. They
> * will recheck the current insn and restart if find_uprobe() fails.
> @@ -676,9 +680,13 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad
> */
> static void delete_uprobe(struct uprobe *uprobe)
> {
> + if (WARN_ON(!uprobe_is_active(uprobe)))
> + return;
> +
> spin_lock(&uprobes_treelock);
> rb_erase(&uprobe->rb_node, &uprobes_tree);
> spin_unlock(&uprobes_treelock);
> + RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
> iput(uprobe->inode);
> put_uprobe(uprobe);
> }
> --
> 1.5.5.1
>



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