[ecasound] Bug report: segfault, etd, time sensitive operations

Hello,

Context:
In the process of adding latency compensation to nama, we are employing
the etd chain-op to create artificial latency so that all tracks in a
chain-setup will be synchronised. The end result is that, once relative
latencies are calculated, we add etd ops where needed with the following
parameters: -etd:x,0,1,100,100, where x substitutes for the required
amount of added latency.

It seems, however, that aadding many such ops in a short period of time
causes ecasound to segfault. Here is the backtrace:
#0 0x0000000000566822 in SAMPLE_ITERATOR_CHANNEL::begin (this=0x7fffd8f60358,
    channel=0) at samplebuffer_iterators.cpp:68
#1 0x0000000000519f0c in EFFECT_DELAY::process (this=0x7fffd8f60330)
    at audiofx_timebased.cpp:209
#2 0x00000000004bebde in CHAIN::process (this=0x7fffd8002e30)
    at eca-chain.cpp:825
#3 0x000000000056082c in ECA_ENGINE::process_chains (this=0x7fffd8012c80)
    at eca-engine.cpp:1699
#4 0x00000000005653c2 in ECA_ENGINE::engine_iteration (this=0x7fffd8012c80)
    at eca-engine.cpp:688
#5 0x000000000053a5c4 in eca_jack_process_engine_iteration (nframes=128,
    arg=0x7fffd800cc40) at audioio_jack_manager.cpp:457
#6 0x000000000053b609 in eca_jack_process_timebase_slave (arg=0x7fffd800cc40,
    nframes=128) at audioio_jack_manager.cpp:565
#7 eca_jack_process_callback (arg=0x7fffd800cc40, nframes=128)
    at audioio_jack_manager.cpp:403
#8 eca_jack_process_callback (nframes=128, arg=0x7fffd800cc40)
    at audioio_jack_manager.cpp:362

The bug is fairly predictibly reproductible under normal conditions,
but, once again, will not occur if supplementary debugging is enabled,
leading me to suspect it is timing dependent.

Attached, you will find ecasound logs chronicling the crash as well as a
log of nama's ECI transactions during the same occurrence.

Cheers,
S.M.

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