On Tue, Nov 01, 2016 at 04:21:36PM +0000, Alex Bennée wrote: > > Paolo Bonzini <pbonz...@redhat.com> writes: > > > On 21/10/2016 13:54, Alex Bennée wrote: > >> There is a slight wart when checking for the state of the BQL when using > >> GThread base co-routines (which we keep for ThreadSanitizer runs). While > >> the main-loop holds the BQL it is suspended until the co-routine > >> completes however the co-routines run in a separate thread so checking > >> the TLS variable could be wrong. > >> > >> We fix this by expanding the check to include qemu_in_coroutine() for > >> GThread based builds. As it is not used for production builds I'm not > >> overly worried about any performance impact which should be negligible > >> anyway. > >> > >> Signed-off-by: Alex Bennée <alex.ben...@linaro.org> > >> Cc: Stefan Hajnoczi <stefa...@redhat.com> > > > > This is wrong unfortunately. It is possible to run coroutines outside > > the BQL (e.g. with -device virtio-blk,iothread=foo). > > > > Do you know exactly why TSAN has no love for coroutines? > > The current production stuff is due to missing support for new stacks > with setcontext. However I have built the latest tsan support library > and that seems happy without the gthread co-routines. > > Currently I'm dealing with glib's racy gthread support however.
I think Paolo suggested we drop the GThread backend on IRC. I agree that we should do that since GThread co-routines break code that uses thread-local variables and have never truly worked. Stefan
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