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J. Bruce Fields
9c335c0b8d
We call svc_xprt_enqueue() after something happens which we think may require handling from a server thread. To avoid such events being lost, svc_xprt_enqueue() must guarantee that there will be a svc_serv() call from a server thread following any such event. It does that by either waking up a server thread itself, or checking that XPT_BUSY is set (in which case somebody else is doing it). But the check of XPT_BUSY could occur just as someone finishes processing some other event, and just before they clear XPT_BUSY. Therefore it's important not to clear XPT_BUSY without subsequently doing another svc_export_enqueue() to check whether the xprt should be requeued. The xpo_wspace() check in svc_xprt_enqueue() breaks this rule, allowing an event to be missed in situations like: data arrives call svc_tcp_data_ready(): call svc_xprt_enqueue(): set BUSY find no write space svc_reserve(): free up write space call svc_enqueue(): test BUSY clear BUSY So, instead, check wspace in the same places that the state flags are checked: before taking BUSY, and in svc_receive(). Signed-off-by: J. Bruce Fields <bfields@redhat.com>