Re: [PATCH] tracing: Have all levels of checks prevent recursion
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2021-10-15 18:20:41
Also in:
linux-riscv, live-patching, lkml
Subsystem:
performance events subsystem, scheduler, the rest, tracing · Maintainers:
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Juri Lelli, Vincent Guittot, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
On Fri, 15 Oct 2021 20:04:29 +0200 Peter Zijlstra [off-list ref] wrote:
On Fri, Oct 15, 2021 at 01:58:06PM -0400, Steven Rostedt wrote:quoted
Something like this:I think having one copy of that in a header is better than having 3 copies. But yes, something along them lines.
I was just about to ask you about this patch ;-)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 4d244e295e85..a6ae329aa654 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h@@ -74,6 +74,27 @@ */ #define FORK_PREEMPT_COUNT (2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) +/** + * interrupt_context_level - return interrupt context level + * + * Returns the current interrupt context level. + * 0 - normal context + * 1 - softirq context + * 2 - hardirq context + * 3 - NMI context + */ +static __always_inline unsigned char interrupt_context_level(void) +{ + unsigned long pc = preempt_count(); + unsigned char level = 0; + + level += !!(pc & (NMI_MASK)); + level += !!(pc & (NMI_MASK | HARDIRQ_MASK)); + level += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)); + + return level; +} + /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ #include <asm/preempt.h>
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index 41f5bfd9e93f..018a04381556 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h@@ -118,12 +118,7 @@ enum { static __always_inline int trace_get_context_bit(void) { - unsigned long pc = preempt_count(); - unsigned char bit = 0; - - bit += !!(pc & (NMI_MASK)); - bit += !!(pc & (NMI_MASK | HARDIRQ_MASK)); - bit += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)); + unsigned char bit = interrupt_context_level(); return TRACE_CTX_NORMAL - bit; }
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 228801e20788..c91711f20cf8 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h@@ -206,11 +206,7 @@ DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user) static inline int get_recursion_context(int *recursion) { unsigned int pc = preempt_count(); - unsigned char rctx = 0; - - rctx += !!(pc & (NMI_MASK)); - rctx += !!(pc & (NMI_MASK | HARDIRQ_MASK)); - rctx += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)); + unsigned char rctx = interrupt_context_level(); if (recursion[rctx]) return -1;
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 15d4380006e3..f6520d0a4c8c 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c@@ -3167,12 +3167,7 @@ static __always_inline int trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) { unsigned int val = cpu_buffer->current_context; - unsigned long pc = preempt_count(); - int bit = 0; - - bit += !!(pc & (NMI_MASK)); - bit += !!(pc & (NMI_MASK | HARDIRQ_MASK)); - bit += !!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)); + int bit = interrupt_context_level(); bit = RB_CTX_NORMAL - bit;