* Completely Remove the option STOP_NMI from the kernel. This option

has proven to have a good effect when entering KDB by using a NMI,
but it completely violates all the good rules about interrupts
disabled while holding a spinlock in other occasions.  This can be the
cause of deadlocks on events where a normal IPI_STOP is expected.
* Adds an new IPI called IPI_STOP_HARD on all the supported architectures.
This IPI is responsible for sending a stop message among CPUs using a
privileged channel when disponible. In other cases it just does match a
normal IPI_STOP.
Right now the IPI_STOP_HARD functionality uses a NMI on ia32 and amd64
architectures, while on the other has a normal IPI_STOP effect. It is
responsibility of maintainers to eventually implement an hard stop
when necessary and possible.
* Use the new IPI facility in order to implement a new userend SMP kernel
function called stop_cpus_hard(). That is specular to stop_cpu() but
it does use the privileged channel for the stopping facility.
* Let KDB use the newly introduced function stop_cpus_hard() and leave
stop_cpus() for all the other cases
* Disable interrupts on CPU0 when starting the process of APs suspension.
* Style cleanup and comments adding

This patch should fix the reboot/shutdown deadlocks many users are
constantly reporting on mailing lists.

Please don't forget to update your config file with the STOP_NMI
option removal

Reviewed by:	jhb
Tested by:	pho, bz, rink
Approved by:	re (kib)

1 files changed, 0 insertions, 1 deletions

diff --git a/sys/i386/conf/NOTES b/sys/i386/conf/NOTES
index f442e24..f772b25 100644
--- a/sys/i386/conf/NOTES
+++ b/sys/i386/conf/NOTES
@@ -49,7 +49,6 @@ options 	MP_WATCHDOG
 
 # Debugging options.
 #
-options 	STOP_NMI		# Stop CPUS using NMI instead of IPI
 options 	COUNT_XINVLTLB_HITS	# Counters for TLB events
 options 	COUNT_IPIS		# Per-CPU IPI interrupt counters