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authorSteven Rostedt <srostedt@redhat.com>2012-05-30 11:43:19 -0400
committerSteven Rostedt <rostedt@goodmis.org>2012-05-31 23:12:20 -0400
commitc0525a6972d3f1fb83058ef503e183475d6e4e26 (patch)
tree38d711db57d8cf4552e42a69fd4a1d1fa082b391
parent8a4d0a687a599f39b7df3fe15f2d51d2157caf44 (diff)
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x86: Reset the debug_stack update counter
When an NMI goes off and it sees that it preempted the debug stack, to keep the debug stack safe, it changes the IDT to point to one that does not modify the stack on breakpoint (to allow breakpoints in NMIs). But the variable that gets set to know to undo it on exit never gets cleared on exit. Thus every NMI will reset it on exit the first time it is done even if it does not need to be reset. [ Added H. Peter Anvin's suggestion to use this_cpu_read/write ] Cc: <stable@vger.kernel.org> # v3.3 Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--arch/x86/kernel/nmi.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 90875279ef3d..a0b2f84457be 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -444,14 +444,16 @@ static inline void nmi_nesting_preprocess(struct pt_regs *regs)
*/
if (unlikely(is_debug_stack(regs->sp))) {
debug_stack_set_zero();
- __get_cpu_var(update_debug_stack) = 1;
+ this_cpu_write(update_debug_stack, 1);
}
}
static inline void nmi_nesting_postprocess(void)
{
- if (unlikely(__get_cpu_var(update_debug_stack)))
+ if (unlikely(this_cpu_read(update_debug_stack))) {
debug_stack_reset();
+ this_cpu_write(update_debug_stack, 0);
+ }
}
#endif