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base: fix deadlock during signal-context dissolve

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This patch moves the removal of the signal context from the
'_platform_finish_dissolve' to the '_platform_begin_dissolve'
method. This is needed because the removal involves taking
the signal-registry lock. The latter must adhere the same
locking order as the code path used for signal delivery.

Fixes #3109
This commit is contained in:
Norman Feske 2019-01-29 15:26:17 +01:00
parent 158650ff01
commit 237d2bff3a
3 changed files with 33 additions and 11 deletions
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7
repos/base-hw/src/lib/base/signal_receiver.cc
View File

@ -82,8 +82,11 @@ void Signal_receiver::_platform_begin_dissolve(Signal_context * const c)
* from taking the lock, and set an invalid context to prevent further
* processing
*/
c->_pending = true;
c->_curr_signal = Signal::Data(nullptr, 0);
{
Lock::Guard context_guard(c->_lock);
c->_pending = true;
c->_curr_signal = Signal::Data(nullptr, 0);
}
Kernel::kill_signal_context(Capability_space::capid(c->_cap));
}

13
repos/base/src/lib/base/signal.cc
View File

@ -318,11 +318,18 @@ void Signal_receiver::dispatch_signals(Signal_source *signal_source)
}
void Signal_receiver::_platform_begin_dissolve(Signal_context *) { }
void Signal_receiver::_platform_begin_dissolve(Signal_context *context)
{
/*
* Because the 'remove' operation takes the registry lock, the context
* must not be locked when calling this method. See the comment in
* 'Signal_receiver::dissolve'.
*/
signal_context_registry()->remove(&context->_registry_le);
}
void Signal_receiver::_platform_finish_dissolve(Signal_context * const c) {
signal_context_registry()->remove(&c->_registry_le); }
void Signal_receiver::_platform_finish_dissolve(Signal_context *) { }
void Signal_receiver::_platform_destructor() { }

24
repos/base/src/lib/base/signal_common.cc
View File

@ -200,8 +200,11 @@ Signal_receiver::~Signal_receiver()
Lock::Guard contexts_lock_guard(_contexts_lock);
/* disassociate contexts from the receiver */
while (_contexts.head())
_unsynchronized_dissolve(_contexts.head());
while (Signal_context *context = _contexts.head()) {
_platform_begin_dissolve(context);
_unsynchronized_dissolve(context);
_platform_finish_dissolve(context);
}
_platform_destructor();
}
@ -209,8 +212,6 @@ Signal_receiver::~Signal_receiver()
void Signal_receiver::_unsynchronized_dissolve(Signal_context * const context)
{
_platform_begin_dissolve(context);
/* tell core to stop sending signals referring to the context */
env_deprecated()->pd_session()->free_context(context->_cap);
@ -220,8 +221,6 @@ void Signal_receiver::_unsynchronized_dissolve(Signal_context * const context)
/* remove context from context list */
_contexts.remove(context);
_platform_finish_dissolve(context);
}
@ -231,13 +230,26 @@ void Signal_receiver::dissolve(Signal_context *context)
throw Context_not_associated();
{
/*
* We must adhere to the following lock-taking order:
*
* 1. Taking the lock for the list of contexts ('_contexts_lock')
* 2. Taking the context-registry lock (this happens inside
* '_platform_begin_dissolve' on platforms that use such a
* registry)
* 3. Taking the lock for an individual signal context
*/
Lock::Guard contexts_lock_guard(_contexts_lock);
_platform_begin_dissolve(context);
Lock::Guard context_lock_guard(context->_lock);
_unsynchronized_dissolve(context);
}
_platform_finish_dissolve(context);
Lock::Guard context_destroy_lock_guard(context->_destroy_lock);
}