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authorSteven Rostedt <srostedt@redhat.com>2012-05-30 17:43:19 +0200
committerSteven Rostedt <rostedt@goodmis.org>2012-06-01 05:12:20 +0200
commitc0525a6972d3f1fb83058ef503e183475d6e4e26 (patch)
tree38d711db57d8cf4552e42a69fd4a1d1fa082b391 /arch/x86
parentftrace: Use breakpoint method to update ftrace caller (diff)
downloadlinux-c0525a6972d3f1fb83058ef503e183475d6e4e26.tar.xz
linux-c0525a6972d3f1fb83058ef503e183475d6e4e26.zip
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>
Diffstat (limited to 'arch/x86')
-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