The main advantage of circular lists (the fact that the head node
has the same memory layout as any other node) is completely negated
by the implementation in qemu-queue.h. Not surprisingly, nobody
uses QCIRCLEQ. While this might change if RCU is ever adopted by
QEMU, the QLIST is also RCU-friendly and in fact it is used in a
RCU-like manner by 9pfs already. So, just kill QCIRCLEQ.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
SynthFS needs a QLIST_INSERT_HEAD_RCU to make sure list instructions are not
re-ordered and therefore avoiding a crash. There may be parallel readers which
should be allowed for lock-free access and this variant allows us to get rid
of rwlocks used by readers.
SynthFS is a special case where we dont really need full RCU capabilities as
it doesnt allow list entry deletion but concurrent readers/writers and
instruction re-ordering should not result in a crash.
Also, once the real rcu is available, dummy rcu macro definitions will go away
and the code will still work as expected.
This patchwork is based on inputs from Paolo Bonzini.
Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Pierre Riteau <Pierre.Riteau@irisa.fr>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Problem: Our file sys-queue.h is a copy of the BSD file, but there are
some additions and it's not entirely compatible. Because of that, there have
been conflicts with system headers on BSD systems. Some hacks have been
introduced in the commits 15cc923584,
f40d753718,
96555a96d7 and
3990d09adf but the fixes were fragile.
Solution: Avoid the conflict entirely by renaming the functions and the
file. Revert the previous hacks.
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Paolo Bonzini