netdev

Qdisc running flag

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.

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

todo

why need busylock?

The values of state.

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

The value of __state.

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

Running flag

check Qdisc running

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

Set Qdisc running

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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 }

Unset Qdisc running

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