Ivykis signal handling
#include <iv_signal.h>
struct iv_signal {
int signum;
unsigned int flags;
void *cookie;
void (*handler)(void *);
};
void IV_SIGNAL_INIT(struct iv_signal *this);
int iv_signal_register(struct iv_signal *this);
void iv_signal_unregister(struct iv_signal *this);
iv_signal provides a way for ivykis(3) applications to handle POSIX signals, by integrating them with the ivykis event loop.
An ivykis application desiring signal notification registers a struct iv_signal object by calling iv_signal_register, after having initialised it with IV_SIGNAL_INIT and subsequently having filled in the ->signum, ->cookie and ->handler members.
Once the signal indicated by ->signum is delivered to any thread in the current process, the callback specified by ->handler is scheduled to be called in the thread that the struct iv_signal object was registered in, with ->cookie as its sole argument.
If the same signal arrives again while the callback function is still running, the callback function is guaranteed to be called again after it returns.
It is permitted to register multiple struct iv_signal objects for the same signal number. If all such objects are registered with IV_SIGNAL_FLAG_EXCLUSIVE in ->flags unset, then all objects will have their callback functions called upon arrival of the signal, in no guaranteed order.
Invoking callback functions stops at the first struct iv_signal object with IV_SIGNAL_FLAG_EXCLUSIVE in ->flags set, so that if all objects have IV_SIGNAL_FLAG_EXCLUSIVE set, only one callback function will be invoked.
To deinitialize a struct iv_signal object, call iv_signal_unregister from the same thread that iv_signal_register was called from on that object.
It is permitted to unregister a struct iv_signal object from any ivykis callback function in the thread it was registered in, including from a callback function triggered by this object, and it is permitted to free the memory corresponding to an unregistered object from its own callback function.
It is guaranteed that signals delivered to child processes that were created by fork(2) but that have not yet called execve(2) will not cause iv_signal callbacks to be invoked in the parent process.
Internally, iv_signal is implemented using iv_event_raw(3).