Re: setnumcapabilities001 failure

Hi Ryan, I don't think that's the issue. Those variables can only be modified in setNumCapabilities, which acquires *all* the capabilities before it makes any changes. There should be no other threads running RTS code(*) while we change the number of capabilities. In particular we shouldn't be in releaseGCThreads while enabled_capabilities is being changed. (*) well except for the parts at the boundary with the external world which run without a capability, such as rts_lock() which acquires a capability. Cheers Simon On 27 Oct 2016 17:10, "Ryan Yates" wrote:

Briefly looking at the code it seems like several global variables involved should be volatile: n_capabilities, enabled_capabilities, and capabilities. Perhaps in a loop like in scheduleDoGC the compiler moves the reads of n_capabilites or capabilites outside the loop. A failed requestSync in that loop would not get updated values for those global pointers. That particular loop isn't doing that optimization for me, but I think it could happen without volatile.

Ryan

On Thu, Oct 27, 2016 at 9:18 AM, Ben Gamari wrote:

...

Simon Marlow writes:

...

I haven't been able to reproduce the failure yet. :(

Indeed I've also not seen it in my own local builds. It's quite an fragile failure.

Cheers,

- Ben

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