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SubjectRe: [RFC PATCH] Kernel Tracepoints (update)
Hi Mathieu,

I found a bug.
Mathieu Desnoyers wrote:
[...]

> +/*
> + * Remove the tracepoint from the tracepoint hash table. Must be called with
> + * mutex_lock held.
> + */
> +static int remove_tracepoint(const char *name)
> +{
> + struct hlist_head *head;
> + struct hlist_node *node;
> + struct tracepoint_entry *e;
> + int found = 0;
> + size_t len = strlen(name) + 1;
> + u32 hash = jhash(name, len-1, 0);
> +
> + head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
> + hlist_for_each_entry(e, node, head, hlist) {
> + if (!strcmp(name, e->name)) {
> + found = 1;
> + break;
> + }
> + }
> + if (!found)
> + return -ENOENT;

before removing, you have to ensure refcount == 0. So,
if (e->refcount != 0)
return -EBUSY;
> + hlist_del(&e->hlist);
> + /* Make sure the call_rcu has been executed */
> + if (e->rcu_pending)
> + rcu_barrier();
> + kfree(e);
> + return 0;
> +}

Thank you,

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com



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