Messages in this thread | | | Date | Thu, 30 Oct 2008 01:34:57 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH 2/2] tracepoint: introduce *_noupdate APIs. |
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* Lai Jiangshan (laijs@cn.fujitsu.com) wrote: > > new APIs separate tracepoint_probe_register(), > tracepoint_probe_unregister() into 2 steps. The first step of them > is just update tracepoint_entry, not connect or disconnect. > > this patch introduce tracepoint_probe_update_all() for update all. > > these APIs are very useful for registering a lots of probes > but just update once only. and a very important thing is that > *_noupdate APIs do not require module_mutex. > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
[...]
> +/** > + * tracepoint_probe_update_all - update tracepoints > + */ > +void tracepoint_probe_update_all(void) > +{ > + LIST_HEAD(release_probes); > + struct tp_probes *pos, *next; > + > + mutex_lock(&tracepoints_mutex); > + if (!need_update) { > + mutex_unlock(&tracepoints_mutex); > + return; > + } > + if (!list_empty(&old_probes)) > + list_replace_init(&old_probes, &release_probes); > + need_update = 0; > + mutex_unlock(&tracepoints_mutex); > + > + tracepoint_update_probes();
I think the read-side of this release_probes list should be protected by the tracepoints_mutex too. Two concurrent tracepoint_probe_update_all() could cause havoc here :
mutex_lock(&tracepoints_mutex);
> + list_for_each_entry_safe(pos, next, &release_probes, u.list) { > + list_del(&pos->u.list); > + call_rcu_sched(&pos->u.rcu, rcu_free_old_probes); > + }
mutex_unlock(&tracepoints_mutex);
?
The rest looks good.
Mathieu
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