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Fix recursive locks when removing procs with a sidechain - #8301

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When removing a plugin-insert that has a sidechain on a bus
that is implicitly soloed the following happens:

 * Route::remove_processor() takes a  WriterLock(_processor_lock)
 * The sidechain input is disconnected
 * Route::sidechain_change_handler() is called which calls
 * Route::input_change_handler()
 * Since the route is implicitly soloed, propagation is attempted
   which calls
 * Route::direct_feeds_according_to_reality()
   which takes ReaderLock(_processor_lock)

Recursive locks, reader-lock after writer-lock don't cause
a deadlock, releasing the reader-lock effectively also
releases the writer-lock...
This commit is contained in:
Robin Gareus 2020-07-11 22:10:43 +02:00
parent 68082abc22
commit 156c1e354a
Signed by: rgareus
GPG Key ID: A090BCE02CF57F04
1 changed files with 27 additions and 37 deletions
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64
libs/ardour/route.cc
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@ -1437,47 +1437,37 @@ Route::remove_processor (boost::shared_ptr<Processor> processor, ProcessorStream
ProcessorState pstate (this);
ProcessorList::iterator i;
bool removed = false;
for (i = _processors.begin(); i != _processors.end(); ) {
if (*i == processor) {
/* move along, see failure case for configure_processors()
where we may need to reconfigure the processor.
*/
/* stop redirects that send signals to JACK ports
from causing noise as a result of no longer being
run.
*/
boost::shared_ptr<IOProcessor> iop = boost::dynamic_pointer_cast<IOProcessor> (*i);
boost::shared_ptr<PluginInsert> pi = boost::dynamic_pointer_cast<PluginInsert>(*i);
if (pi != 0) {
assert (iop == 0);
iop = pi->sidechain();
}
if (iop != 0) {
iop->disconnect ();
}
i = _processors.erase (i);
removed = true;
break;
} else {
++i;
}
}
if (!removed) {
ProcessorList::iterator i = find (_processors.begin(), _processors.end(), processor);
if (i == _processors.end ()) {
/* what? */
return 1;
}
_processors.erase (i);
/* stop redirects that send signals to JACK ports
* from causing noise as a result of no longer being run
*/
boost::shared_ptr<IOProcessor> iop = boost::dynamic_pointer_cast<IOProcessor> (*i);
boost::shared_ptr<PluginInsert> pi = boost::dynamic_pointer_cast<PluginInsert>(*i);
if (pi != 0) {
assert (iop == 0);
iop = pi->sidechain();
}
if (iop != 0) {
/* This calls Route::sidechain_change_handler -> Route::input_change_handler()
* When the route is implicitly soloed this further calls
* Route::direct_feeds_according_to_reality() which takes a
* ReaderLock (_processor_lock). So we need to release the lock first.
*/
lm.release ();
iop->disconnect ();
lm.acquire ();
}
if (configure_processors_unlocked (err, &lm)) {
pstate.restore ();
/* we know this will work, because it worked before :) */