5.15-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (VMware) rostedt@goodmis.org
[ 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.kick...
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 --- include/linux/trace_recursion.h | 11 ++++++----- kernel/trace/ring_buffer.c | 12 ++++++------ 2 files changed, 12 insertions(+), 11 deletions(-)
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h index fe95f09225266..00acd7dca7a7d 100644 --- a/include/linux/trace_recursion.h +++ b/include/linux/trace_recursion.h @@ -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 diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index e5dc7b5a261c6..c3c9960c9f27b 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -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)))) { /*