From 7b4a33f0526d0f3a8a902d136131f0d53da362f7 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 30 May 2012 11:43:19 -0400 Subject: [PATCH] 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: # v3.3 Signed-off-by: Steven Rostedt --- arch/x86/kernel/nmi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 90875279ef3d5..a0b2f84457beb 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 -- 2.39.5