[PATCH] NMI: Update NMI users of RCU to use new API

Uses of RCU for dynamically changeable NMI handlers need to use the new
rcu_dereference() and rcu_assign_pointer() facilities.  This change makes
it clear that these uses are safe from a memory-barrier viewpoint, but the
main purpose is to document exactly what operations are being protected by
RCU.  This has been tested on x86 and x86-64, which are the only
architectures affected by this change.

Signed-off-by: <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 4 insertions, 4 deletions

diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 54629bb5893a..029bf94cda7d 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -657,7 +657,7 @@ fastcall void do_nmi(struct pt_regs * regs, long error_code)
 
         ++nmi_count(cpu);
 
-        if (!nmi_callback(regs, cpu))
+        if (!rcu_dereference(nmi_callback)(regs, cpu))
                 default_do_nmi(regs);
 
         nmi_exit();
@@ -665,7 +665,7 @@ fastcall void do_nmi(struct pt_regs * regs, long error_code)
 
 void set_nmi_callback(nmi_callback_t callback)
 {
-        nmi_callback = callback;
+        rcu_assign_pointer(nmi_callback, callback);
 }
 EXPORT_SYMBOL_GPL(set_nmi_callback);
 
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 84cae81fff8b..caf164959e19 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -524,14 +524,14 @@ asmlinkage void do_nmi(struct pt_regs * regs, long error_code)
 
         nmi_enter();
         add_pda(__nmi_count,1);
-        if (!nmi_callback(regs, cpu))
+        if (!rcu_dereference(nmi_callback)(regs, cpu))
                 default_do_nmi(regs);
         nmi_exit();
 }
 
 void set_nmi_callback(nmi_callback_t callback)
 {
-        nmi_callback = callback;
+        rcu_assign_pointer(nmi_callback, callback);
 }
 
 void unset_nmi_callback(void)