#ifndef _THREAD_H
#define _THREAD_H
+#include <signal.h>
#include <pthread.h>
-// A rather generic thread class with start/stop functionality.
-// NOTE: stop is somewhat racy (there's no guaranteed breakout from syscalls),
-// since signals don't stick. We'll need to figure out something more
-// intelligent later, probably based on sending a signal to an fd.
+struct timespec;
+
+// A thread class with start/stop and signal functionality.
+//
+// SIGUSR1 is blocked during execution of do_work(), so that you are guaranteed
+// to receive it when doing wait_for_activity(), and never elsewhere. This means
+// that you can test whatever status flags you'd want before calling
+// wait_for_activity(), and then be sure that it actually returns immediately
+// if a SIGUSR1 (ie., wakeup()) happened, even if it were sent between your test
+// and the wait_for_activity() call.
class Thread {
public:
+ virtual ~Thread();
void run();
void stop();
protected:
- // Recovers the this pointer, and calls do_work().
+ // Recovers the this pointer, blocks SIGUSR1, and calls do_work().
static void *do_work_thunk(void *arg);
virtual void do_work() = 0;
- volatile bool should_stop;
+ // Waits until there is activity of the given type on <fd> (or an error),
+ // or until a wakeup. Returns true if there was actually activity on
+ // the file descriptor.
+ //
+ // If fd is -1, wait until a wakeup or timeout.
+ // if timeout_ts is NULL, there is no timeout.
+ bool wait_for_activity(int fd, short events, const timespec *timeout_ts);
+
+ // Wait until a wakeup.
+ void wait_for_wakeup(const timespec *timeout_ts) { wait_for_activity(-1, 0, timeout_ts); }
+
+ // Make wait_for_activity() return. Note that this is a relatively expensive
+ // operation.
+ void wakeup();
+
+ bool should_stop();
+
+ // The signal set as it were before we blocked SIGUSR1.
+ sigset_t sigset_without_usr1_block;
private:
pthread_t worker_thread;
+
+ // Protects should_stop_status.
+ pthread_mutex_t should_stop_mutex;
+
+ // If this is set, the thread should return as soon as possible from do_work().
+ bool should_stop_status;
};
#endif // !defined(_THREAD_H)