Qdisc running flag

0.0.1. Summary

In struct Qdisc, there are two similar fileds.
running flag is stored in __state of struct Qdisc, NOT state.
Every time, when we send a packet from qdisc, the running flag is
set by qdisc_run_begin, and after that, it is removed by qdisc_run_end.

84         unsigned long           state;
...
87         unsigned int            __state;

0.0.1.1. todo

why need busylock?

0.0.1.2. The values of state.

24 enum qdisc_state_t {
25         __QDISC_STATE_SCHED,
26         __QDISC_STATE_DEACTIVATED,
27         __QDISC_STATE_THROTTLED,
28 };

0.0.1.3. The value of __state.

33 enum qdisc___state_t {
34         __QDISC___STATE_RUNNING = 1,
35 };

0.1. Running flag

0.1.1. check Qdisc running

96 static inline bool qdisc_is_running(const struct Qdisc *qdisc)
97 {
98         return (qdisc->__state & __QDISC___STATE_RUNNING) ? true : false;
99 }

0.1.2. Set Qdisc running

101 static inline bool qdisc_run_begin(struct Qdisc *qdisc)
102 {
103         if (qdisc_is_running(qdisc))
104                 return false;
105         qdisc->__state |= __QDISC___STATE_RUNNING;
106         return true;
107 }

0.1.3. Unset Qdisc running

109 static inline void qdisc_run_end(struct Qdisc *qdisc)
110 {
111         qdisc->__state &= ~__QDISC___STATE_RUNNING;
112 }