Messages in this thread | | | Date | Thu, 30 Oct 2008 01:39:49 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH 2/2] tracepoint: introduce *_noupdate APIs. |
| |
* Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote: > * 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. >
Argh, forget it. LIST_HEAD(release_probes); is local to the function, there is nothing to protect here. My eyes thought they saw a "static" here for some reason. Night shift....
The patch is good as-is.
Thanks !
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Mathieu > > -- > Mathieu Desnoyers > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
| |