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perf: Optimize get_recursion_context() 

"Look ma, no branches!"

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lkml.kernel.org/r/20201030151955.187580298@infradead.org
This commit is contained in:
Peter Zijlstra 2020-10-30 13:43:16 +01:00
parent ce0f17fc93
commit 09da9c8125
1 changed files with 5 additions and 9 deletions
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14
kernel/events/internal.h
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@ -205,16 +205,12 @@ DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
static inline int get_recursion_context(int *recursion)
{
int rctx;
unsigned int pc = preempt_count();
unsigned char rctx = 0;
if (unlikely(in_nmi()))
rctx = 3;
else if (in_irq())
rctx = 2;
else if (in_serving_softirq())
rctx = 1;
else
rctx = 0;
rctx += !!(pc & (NMI_MASK));
rctx += !!(pc & (NMI_MASK | HARDIRQ_MASK));
rctx += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET));
if (recursion[rctx])
return -1;