ardour/livetrax
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Fix potential deadlock when adding sidechain port

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Previously add_remove_sidechain() released the process-lock
(to create the I/O ports), while keeping a processor writer-lock.

Meanwhile the auto-connect thread may be woken up to perform
a latency update. This thread takes the process-lock and
then stalls, waiting for a processor reader-lock.

Then add_remove_sidechain() continues and tries to re-acquire
the process-lock.
This commit is contained in:
Robin Gareus 2020-06-26 17:46:34 +02:00
parent 0518e1e88f
commit a0bdf87720
Signed by: rgareus
GPG Key ID: A090BCE02CF57F04
1 changed files with 8 additions and 7 deletions
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15
libs/ardour/route.cc
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@ -2256,7 +2256,7 @@ Route::reorder_processors (const ProcessorList& new_order, ProcessorStreams* err
bool
Route::add_remove_sidechain (boost::shared_ptr<Processor> proc, bool add)
{
if (_session.actively_recording ()) {
if (_session.actively_recording () || _in_sidechain_setup) {
return false;
}
@ -2278,11 +2278,8 @@ Route::add_remove_sidechain (boost::shared_ptr<Processor> proc, bool add)
}
{
Glib::Threads::Mutex::Lock lx (AudioEngine::instance()->process_lock ()); // take before Writerlock to avoid deadlock
Glib::Threads::RWLock::WriterLock lm (_processor_lock);
PBD::Unwinder<bool> uw (_in_sidechain_setup, true);
lx.release (); // IO::add_port() and ~IO takes process lock - XXX check if this is safe
if (add) {
if (!pi->add_sidechain ()) {
return false;
@ -2293,11 +2290,15 @@ Route::add_remove_sidechain (boost::shared_ptr<Processor> proc, bool add)
}
}
lx.acquire ();
Glib::Threads::Mutex::Lock lx (AudioEngine::instance()->process_lock ()); // take before Writerlock to avoid deadlock
Glib::Threads::RWLock::WriterLock lm (_processor_lock);
list<pair<ChanCount, ChanCount> > c = try_configure_processors_unlocked (n_inputs (), 0);
lx.release ();
if (c.empty()) {
lm.release ();
lx.release ();
if (add) {
pi->del_sidechain ();
} else {
@ -2306,7 +2307,7 @@ Route::add_remove_sidechain (boost::shared_ptr<Processor> proc, bool add)
}
return false;
}
lx.acquire ();
configure_processors_unlocked (0, &lm);
}