Messages in this thread | | | Date | Fri, 31 Oct 2008 00:14:19 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/2] tracepoint: introduce *_noupdate APIs. |
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* Mathieu Desnoyers <compudj@krystal.dyndns.org> wrote:
> * 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>
ok, i've applied both patches to tip/tracing/tracepoints:
57bc8ea: tracepoint: introduce *_noupdate APIs. bbec237: tracepoint: simplification for tracepoints using RCU
thanks!
(Note, i had to resolve conflicts, hopefully i got the end result right. Please double-check tip/master.)
Ingo
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