tgl_timer_methods.insert called too often about tgl HOT 8 OPEN

Calling tgl_timer_insert multiple times shouldn't be an issue.

What the function appears to do is to iterate through all running queries to restart them. The reason why the function shows up multiple times is that tree.h implements it as a recursive function (https://github.com/vysheng/tgl/blob/master/tree.h#L133-L147).

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There's something off about this. The issue appears to be caused by an assertion assert (-1 == t->fd), which is an assertion I'm not able to find anywhere in the code.

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Of course it is an issue:

• instantiation
• call with insert, internal fd is set to
• another call with insert, internal fd is set to
• call to free, internal freeing stops the timer, but NOT the one.
• timer fires, doing a use-after-free

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That assertion is written by me.

I'm making the assumption that when insert is called, there should be no other timer currently being "ticking"

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You are right, of course it shouldn't be called multiple times on the same timer_alarm struct.

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I've debugged this issue and printed a stacktrace for every time timer insert is called, while using the same assertion as Ben.

https://gist.github.com/majn/0c69dd738d7690222489

Apparently, tgl_do_get_difference is executed for the first time and starts the regular alarm timeout of (6 seconds) and then when work_new_session_created is received, the second timeout (0.001s) is called on the same struct.

@vysheng Is this behavior by design and the timer implementation is supposed to cancel all pending timeouts on its own?

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One more thing:

work_new_session_created appears to happen every time the tgl is started, restarting all running queries on every restart.

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From @vysheng: The intended meaning of that was precisely like we assumed.

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