On 09/14/2017 02:50 AM, Peter Xu wrote: > This is not a problem if we are only having one single loop thread like > before. However, after per-monitor thread is introduced, this is not > true any more, and the race can happen. > > The race can be triggered with "make check -j8" sometimes: > > qemu-system-x86_64: /root/git/qemu/chardev/char-io.c:91: > io_watch_poll_finalize: Assertion `iwp->src == NULL' failed. > > This patch keeps the reference for the watch object when creating in > io_add_watch_poll(), so that the object will never be released in the > context main loop, especially when the context loop is running in > another standalone thread. Meanwhile, when we want to remove the watch > object, we always first detach the watch object from its owner context, > then we continue with the cleanup. > > Without this patch, calling io_remove_watch_poll() in main loop thread > is not thread-safe, since the other per-monitor thread may be modifying > the watch object at the same time. > > Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com> > Signed-off-by: Peter Xu <pet...@redhat.com> > ---
> + * Let's blame the glib bug mentioned in commit 2b3167 (again) for That 6-char commit id may become ambiguous soon (it's still rare to see ambiguity with an 8-char id, although I've seen it more in recent times than in the past; and git itself has moved from a 7-char default abbreviation length in the 2.0 days to what is now a 10-char default abbreviation in 2.13.5). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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