Assertion failure when using multithreading in debug mode.

Using the -debug compiler option in search of a (hopefully unrelated) bug, I've begun to receive the following error message a few seconds after starting my program;

Multi: internal error: ASSERTION FAILED: file rts/Schedule.c, line 1311

    (GHC version 7.6.2 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Aborted

When I have time and if this site allows, I'll try to find what precisely in my code is generating the error and add that to this ticket. Until then, what information I can give:

Running the same executable in non-threaded mode (executing with "+RTS N1" rather than "+RTS N2" or greater) produces no error.
The program calls into C using the FFI interface, and there is also a callback from C back into Haskell. This would be happening around when the error occurs.
For reasons I presume to have to do with the C++ code, the program segfaults after extended execution; this is the hopefully unrelated bug I was after when I found this.

Trac metadata

Trac field	Value
Version	7.6.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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Assertion failure when using multithreading in debug mode.