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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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