* 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, 2 insertions, 4 deletions

diff --git a/sys/i386/include/smp.h b/sys/i386/include/smp.h
index 917c285..968cdb4 100644
--- a/sys/i386/include/smp.h
+++ b/sys/i386/include/smp.h
@@ -60,7 +60,8 @@ inthand_t
 void	cpu_add(u_int apic_id, char boot_cpu);
 void	cpustop_handler(void);
 void	init_secondary(void);
-void	ipi_selected(u_int cpus, u_int ipi);
+int	ipi_nmi_handler(void);
+void	ipi_selected(cpumask_t cpus, u_int ipi);
 void	ipi_all_but_self(u_int ipi);
 #ifndef XEN
 void 	ipi_bitmap_handler(struct trapframe frame);
@@ -76,9 +77,6 @@ void	smp_masked_invlpg_range(cpumask_t mask, vm_offset_t startva,
 void	smp_invltlb(void);
 void	smp_masked_invltlb(cpumask_t mask);
 
-#ifdef STOP_NMI
-int	ipi_nmi_handler(void);
-#endif
 #ifdef XEN
 void ipi_to_irq_init(void);