From: "Paul E. McKenney" <paulmck@us.ibm.com>
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>
---
arch/i386/kernel/traps.c | 4 ++--
arch/x86_64/kernel/nmi.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff -puN arch/i386/kernel/traps.c~nmi-update-nmi-users-of-rcu-to-use-new-api arch/i386/kernel/traps.c
--- devel/arch/i386/kernel/traps.c~nmi-update-nmi-users-of-rcu-to-use-new-api 2005-08-06 15:34:45.000000000 -0700
+++ devel-akpm/arch/i386/kernel/traps.c 2005-08-06 15:34:45.000000000 -0700
@@ -657,7 +657,7 @@ fastcall void do_nmi(struct pt_regs * re
++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 * re
void set_nmi_callback(nmi_callback_t callback)
{
- nmi_callback = callback;
+ rcu_assign_pointer(nmi_callback, callback);
}
EXPORT_SYMBOL_GPL(set_nmi_callback);
diff -puN arch/x86_64/kernel/nmi.c~nmi-update-nmi-users-of-rcu-to-use-new-api arch/x86_64/kernel/nmi.c
--- devel/arch/x86_64/kernel/nmi.c~nmi-update-nmi-users-of-rcu-to-use-new-api 2005-08-06 15:34:45.000000000 -0700
+++ devel-akpm/arch/x86_64/kernel/nmi.c 2005-08-06 15:34:45.000000000 -0700
@@ -524,14 +524,14 @@ asmlinkage void do_nmi(struct pt_regs *
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)
_