On Tue, Jan 27, 2009 at 02:47:27PM +0100, Oliver Neukum ([email protected])
wrote:
> > > +static inline int rds_conn_is_sending(struct rds_connection *conn)
> > > +{
> > > + int ret = 0;
> > > +
> > > + if (!mutex_trylock(&conn->c_send_lock))
> > > + ret = 1;
> > > + else
> > > + mutex_unlock(&conn->c_send_lock);
> > > +
> > > + return ret;
> > > +}
> > > +
> >
> > This one is eventually invoked under the spin_lock with turned off irqs,
> > which may freeze the machine:
> > rds_for_each_conn_info() -> spin_lock_irqsave(global lock) ->
> > rds_conn_info_visitor() -> rds_conn_info_set() -> rds_conn_is_sending()
> > -> boom.
>
> Why? This is _trylock. It won't block.
Unlock may reschedule.
--
Evgeniy Polyakov
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