PR 6504

[Frank Ch. Eigler]

Masami Hiramatsu <mhiramat@redhat.com> writes:

> [...]  Actually, relay_switch_subbuf() doesn't call any kernel
> functions except __mod_timer (others are primitive inlines or
> macros). so, with current patch which is for systemtap runtime, you
> don't need to update the blacklist.

That's good.  The patch attached to bug #6504 looks plausible - I'm
not a utt/runtime expert - but I'm worried by a few things.  It seems
like there are several possible races (utt->wakeup being set/cleared;
_utt_wakeup_readers:waitqueue_active vs.  wake_up_interruptible), and
the UTT_TIMER_INTERVAL seems too small as an unconditional poll.  (I
wonder the same thing about STP_WORK_TIMER in
runtime/transport/transport.c.)

To what extent could a delayed-work backend simplify this code?  (If
that subsystem needs to be blacklisted, so be it.)

- FChE