On Tue, Jan 27, 2009 at 8:28 AM, Steve Wise [off-list ref] wrote:

Oliver Neukum wrote:

quoted

Am Tuesday 27 January 2009 14:34:19 schrieb Evgeniy Polyakov:

quoted

On Mon, Jan 26, 2009 at 06:17:43PM -0800, Andy Grover
(andy.grover@oracle.com) wrote:

quoted

+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.

mutex_trylock() uses spin_lock_mutex() which has this in the debug version:

DEBUG_LOCKS_WARN_ON(in_interrupt());

What's the best way to fix this?

This is all so rds-info can print out a nice list of connections, and
if they're sending or not. I don't see an easy way to fix this. A
_trylock-like function that didn't grab it would be nice? I can always
just not report this particular bit of info, that actually might be
easiest.

Regards -- Andy