KVM: PPC: Book 3S: XICS: Fix potential issue with duplicate IRQ resends
BugLink: http://bugs.launchpad.net/bugs/1651248
It is possible that in the following order, one irq is resent twice:
CPU 1 CPU 2
ics_check_resend()
lock ics_lock
see resend set
unlock ics_lock
/* change affinity of the irq */
kvmppc_xics_set_xive()
write_xive()
lock ics_lock
see resend set
unlock ics_lock
icp_deliver_irq() /* resend */
icp_deliver_irq() /* resend again */
It doesn't have any user-visible effect at present, but needs to be avoided
when the following patch implementing the P/Q stuff is applied.
This patch clears the resend flag before releasing the ics lock, when we
know we will do a re-delivery after checking the flag, or setting the flag.
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
(cherry picked from linux-next commit
bf5a71d53835110d46d33eb5335713ffdbff9ab6)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>