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tracing: Reuse logic from perf's get_recursion_context()

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[ Upstream commit 9b84fadc444de5456ab5f5487e2108311c724c3f ]

Instead of having branches that adds noise to the branch prediction, use
the addition logic to set the bit for the level of interrupt context that
the state is currently in. This copies the logic from perf's
get_recursion_context() function.

Link: https://lore.kernel.org/all/20211015161702.GF174703@worktop.programming.kicks-ass.net/

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Stable-dep-of: 87c3a5893e86 ("sched/core: Optimize in_task() and in_interrupt() a bit")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Steven Rostedt (VMware) 2021-10-15 13:42:40 -04:00 committed by Greg Kroah-Hartman
parent 670b3e902f
commit 48fef664d7
2 changed files with 12 additions and 11 deletions
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11
include/linux/trace_recursion.h
View File

@ -117,12 +117,13 @@ enum {
static __always_inline int trace_get_context_bit(void)
{
unsigned long pc = preempt_count();
unsigned char bit = 0;
if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
return TRACE_CTX_NORMAL;
else
return pc & NMI_MASK ? TRACE_CTX_NMI :
pc & HARDIRQ_MASK ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ;
bit += !!(pc & (NMI_MASK));
bit += !!(pc & (NMI_MASK | HARDIRQ_MASK));
bit += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET));
return TRACE_CTX_NORMAL - bit;
}
#ifdef CONFIG_FTRACE_RECORD_RECURSION

12
kernel/trace/ring_buffer.c
View File

@ -3250,13 +3250,13 @@ trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned int val = cpu_buffer->current_context;
unsigned long pc = preempt_count();
int bit;
int bit = 0;
if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
bit = RB_CTX_NORMAL;
else
bit = pc & NMI_MASK ? RB_CTX_NMI :
pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
bit += !!(pc & (NMI_MASK));
bit += !!(pc & (NMI_MASK | HARDIRQ_MASK));
bit += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET));
bit = RB_CTX_NORMAL - bit;
if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
/*