[Bug runtime/3858] option to share trace buffers between probe modules

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2007-10-17 23:02 -------
Interesting solution (using module-exported functions from the host module)!
Martin, if you have no objection, let's go ahead.

One additional consideration for testing/checking: this now makes it theoretically
possible for distinct probes to call into one particular probe module's runtime
at the same time.  Even though this is limited to the I/O functions, can you
cover whether any additional mutual exclusion may be necessary?  Even on per-cpu
buffers, we have situations where probes don't run atomically any more ("begin" 
probes that don't block interrupts, only preemption).  So if the host does a

 probe begin { while(i++<1000) { log ("lots of stuff") } }

at the same time the guest does

 probe timer.profile { log ("some stuff") }

then could we have a problem?

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http://sourceware.org/bugzilla/show_bug.cgi?id=3858

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