Commit-ID: c0525a6972d3f1fb83058ef503e183475d6e4e26
Gitweb: http://git.kernel.org/tip/c0525a6972d3f1fb83058ef503e183475d6e4e26
Author: Steven Rostedt <srostedt@xxxxxxxxxx>
AuthorDate: Wed, 30 May 2012 11:43:19 -0400
Committer: Steven Rostedt <rostedt@xxxxxxxxxxx>
CommitDate: Thu, 31 May 2012 23:12:20 -0400
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@xxxxxxxxxxxxxxx> # v3.3
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
arch/x86/kernel/nmi.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 9087527..a0b2f84 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
--
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