When you get the "thread blocked indefinitely in an STM transaction" it is the result of the garbage collector finding no references to the TVars that a 'retry'ing or blocked transaction. If there are no references to those TVars then there is no way for that transaction to ever succeed. I don't know if that helps.

On Wed, Feb 4, 2015 at 7:59 AM, Magicloud Magiclouds <magicloud.magiclouds@gmail.com> wrote:

Hi,

I met an issue while I was using xhb. When a certain property of root window being changed, it was supposed to give me an AccessError. But actually I got "thread blocked indefinitely in an STM transaction" when I waitForEvent.

AFAIK, in xhb, it forks a thread to read what X server sends. Then parse and put it into a TChan. waitForEvent reads from the TChan.

It is reasonable to me that if X server did not send anything, then waitForEvent would be blocked. But apparently there are some other policies in RTS.

So what is that? And how should I debug it?

--
竹密岂妨流水过
山高哪阻野云飞

And for G+, please use magiclouds#gmail.com.

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