Github user shenzhang920 commented on the pull request:
https://github.com/apache/trafficserver/pull/603#issuecomment-215265241
Description:
When calling TSContSchedule()/TSContScheduleEvery(), the passed in
parameter TSCont have to have MUTEX; otherwise if we call
TSContSchedule()/TSContScheduleEvery() more than once using same TSCont, only
the first call will take effect; all the following schedule are ignored due to
MUTEX issue.
Root casue:
The first time calling TSHttpSchedule() with TSCont A (and TSCont A doesn't
have a mutex), it creates Event A, assign thread A; while calling
EThread::schedule(), e->continuation->mutex is NULL, so "e->mutex =
e->continuation->mutex = e->ethread->mutex;" is executed.
Now Event A's mutex = TSCont A's mutex = thread A's mutex
The second time calling TSHttpSchedule() with TSCont A, it creates Event B,
assign thread B;
while calling EThread::schedule(), e->continuation->mutex is NOT NULL, so
"e->mutex = e->continuation->mutex;" is executed.
Now Event B's mutex = TSCont A's mutex (which actually is Event A's mutex)
Eventually, EventA and EventB use a same mutex which causes the second
scheduling get ignored.
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