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Peter Maydell authored
A gcc codegen bug in x86_64-w64-mingw32-gcc (GCC) 4.6.3 means that non-debug builds of QEMU for Windows tend to assert when using coroutines. Work around this by marking qemu_coroutine_switch as noinline. If we allow gcc to inline qemu_coroutine_switch into coroutine_trampoline, then it hoists the code to get the address of the TLS variable "current" out of the while() loop. This is an invalid transformation because the SwitchToFiber() call may be called when running thread A but return in thread B, and so we might be in a different thread context each time round the loop. This can happen quite often. Typically. a coroutine is started when a VCPU thread does bdrv_aio_readv: VCPU thread main VCPU thread coroutine I/O coroutine bdrv_aio_readv -----> start I/O operation thread_pool_submit_co <------------ yields ...
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