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Post signal-handler hook in entrypoint

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A Signal_handler may schedule a hook function that is executed after the
signal handler returned. This can be used if the hook function may
trigger a (nested) signal handler by means of
wait_and_dispatch_one_signal(). Otherwise, an occurrence of the same
signal that triggered the original signal handler results in a dead lock
just before calling the nested handler (due to the Signal_context
destruction lock).
This commit is contained in:
Christian Helmuth 2017-02-10 23:21:59 +01:00 committed by Norman Feske
parent b805e001db
commit 6e5f3d432e
1 changed files with 33 additions and 2 deletions
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35
repos/base/include/base/entrypoint.h
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@ -30,6 +30,13 @@ namespace Genode {
class Genode::Entrypoint : Genode::Noncopyable
{
public:
/**
* Functor for post signal-handler hook
*/
struct Post_signal_hook { virtual void function() = 0; };
private:
struct Signal_proxy
@ -46,10 +53,13 @@ class Genode::Entrypoint : Genode::Noncopyable
void signal()
{
/* XXX introduce while-pending loop */
try {
Signal sig = ep._sig_rec->pending_signal();
ep._dispatch_signal(sig);
} catch (Signal_receiver::Signal_not_pending) { }
ep._execute_post_signal_hook();
}
};
@ -79,6 +89,16 @@ class Genode::Entrypoint : Genode::Noncopyable
void (*_suspended_callback) () = nullptr;
void (*_resumed_callback) () = nullptr;
Post_signal_hook *_post_signal_hook = nullptr;
void _execute_post_signal_hook()
{
if (_post_signal_hook != nullptr)
_post_signal_hook->function();
_post_signal_hook = nullptr;
}
/*
* This signal handler is solely used to force an iteration of the
* signal-dispatch loop. It is triggered by 'schedule_suspend' to
@ -146,8 +166,11 @@ class Genode::Entrypoint : Genode::Noncopyable
*/
void wait_and_dispatch_one_signal()
{
Signal sig = _sig_rec->wait_for_signal();
_dispatch_signal(sig);
{
Signal sig = _sig_rec->wait_for_signal();
_dispatch_signal(sig);
}
_execute_post_signal_hook();
}
/**
@ -162,6 +185,14 @@ class Genode::Entrypoint : Genode::Noncopyable
* state, while 'resumed is called when the entrypoint is fully functional again.
*/
void schedule_suspend(void (*suspended)(), void (*resumed)());
/**
* Register hook functor to be called after signal was handled
*/
void schedule_post_signal_hook(Post_signal_hook *hook)
{
_post_signal_hook = hook;
}
};
#endif /* _INCLUDE__BASE__ENTRYPOINT_H_ */