uprobes: Introduce uprobe_is_active()
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: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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@ -669,6 +669,10 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad
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return set_orig_insn(&uprobe->arch, mm, vaddr);
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}
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static inline bool uprobe_is_active(struct uprobe *uprobe)
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{
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return !RB_EMPTY_NODE(&uprobe->rb_node);
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}
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/*
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* There could be threads that have already hit the breakpoint. They
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* will recheck the current insn and restart if find_uprobe() fails.
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@ -676,9 +680,13 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad
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*/
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static void delete_uprobe(struct uprobe *uprobe)
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{
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if (WARN_ON(!uprobe_is_active(uprobe)))
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return;
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spin_lock(&uprobes_treelock);
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rb_erase(&uprobe->rb_node, &uprobes_tree);
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spin_unlock(&uprobes_treelock);
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RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
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iput(uprobe->inode);
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put_uprobe(uprobe);
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}
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