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authorBjörn Gustavsson <[email protected]>2014-03-07 10:41:32 +0100
committerBjörn Gustavsson <[email protected]>2014-03-20 13:10:36 +0100
commit9327904dcbf2708823c05baa7532783fb0214792 (patch)
treed5f157e885b0ccdbe63f95173df72425f1a9d468 /lib/compiler
parent544fb141916d8676bc763318074e4d0783414af1 (diff)
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Teach the call_time trace to notice when the trace dies (non-SMP system)
The call_time trace is a special kind of tracing that requires a tracer process just like ordinary call trace, but it never actually sends anything to the tracer. It merely use the existence of a trace process (and call trace flags) as an indication that call_time tracing is active for the process. If the tracer dies in a non-SMP run-time system, processes with call_time tracing would not notice that the tracer had died. Furthermore, if the set_on_spawn flag was active, the dead tracer could be propagaged to newly spawned processes. Before accumulating trace information in a non-SMP system, always validate the tracer process. (In an SMP system, a reference to a dead tracer will be cleared away each time a process is scheduled.) While we could put all of the new code beam_bp.c, we have chosen to make a function call from beam_bp.c to a function in erl_trace.c for clarity's sake and to ease further maintenance. In the future, we might want to handle tracing in more similar ways in the SMP and non-SMP system.
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