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-rw-r--r--arch/x86_64/kernel/entry.S7
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 4fcc0ad8bbe..ea32688386f 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -519,7 +519,12 @@ END(stub_rt_sigreturn)
testl $3,CS(%rdi)
je 1f
swapgs
-1: incl %gs:pda_irqcount # RED-PEN should check preempt count
+ /* irqcount is used to check if a CPU is already on an interrupt
+ stack or not. While this is essentially redundant with preempt_count
+ it is a little cheaper to use a separate counter in the PDA
+ (short of moving irq_enter into assembly, which would be too
+ much work) */
+1: incl %gs:pda_irqcount
cmoveq %gs:pda_irqstackptr,%rsp
push %rbp # backlink for old unwinder
/*