[Qemu-devel] [Bug 883136] Re: qemu on ARM hosts aborts on startup because makecontext() always fails

[Peter Maydell]

http://comments.gmane.org/gmane.comp.lib.glibc.ports/1325

-- Michael's version of the makecontext patches has been committed to
glibc-ports and should be available in glibc 2.16.

Upstream qemu (and thus qemu-linaro) now have a version of the configure
check which tests for __stub_makecontext, so qemu will just
automatically pick up the makecontext implementation when compiled
against a glibc which supports it. So I think the only remaining thing
is to decide whether Linaro and/or Ubuntu want to backport this.

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https://bugs.launchpad.net/bugs/883136

Title:
  qemu on ARM hosts aborts on startup because makecontext() always fails

Status in QEMU:
  Fix Committed
Status in Linaro QEMU:
  Fix Committed

Bug description:
  qemu has recently grown a coroutines implementation. There are two
  versions, one using the makecontext/setcontext/swapcontext functions
  from ucontext.h, and one falling back to implementing coroutines as
  separate glib threads. configure chooses the former if the platform
  has a makecontext().

  Unfortunately ARM eglibc provides a makecontext() which always fails
  ENOSYS, which means the configure check passes but when qemu starts it
  abort()s.

  The best fix for this is probably going to involve making the
  coroutine implementation runtime-selectable.

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