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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-08-09 06:14:34 +02:00
Steven Rostedt
1e67bb60bb
Tracepoints require that RCU is watching. To prevent them from being used in places that RCU is not watching, the trace_##event() macro always calls rcu_is_watching() even when the event is not enabled and warns if RCU is not watching. This is to make sure a warning is triggered even if the tracepoint is never enabled (as it is only a bug when it is). It was noticed that tracepoints could be hidden within trace_#event#_enabled() calls, which are used to do extra work for the tracepoint only if the tracepoint is enabled. But this also can hide the fact that a tracepoint is placed in a location that can be called when RCU is not watching. Commit9764e731ef("tracepoint: Add lockdep rcu_is_watching() check to trace_##name##_enabled()") added a check to the trace_##event##_enabled() macro to make sure RCU is watching when it is called to make sure not to hide the bug of a tracepoint being called when RCU is not watching. There is one case in the irq_disable tracepoint where it is within a trace_irq_disable_enabled() block, but it checks if RCU is watching, and if it isn't, it makes a call to ct_irq_enter() that makes RCU watch again. But because trace_irq_disable_enabled() now checks if RCU is watching and will trigger if it isn't. This is a false warning as the code within the block handles this case. Add a new internal macro __trace_##event##_enabled() that doesn't check if RCU is watching, and convert the irq_enable/disable tracepoints over to it. Link: https://patch.msgid.link/20260701132744.6a7fc68b@robin Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Closes: https://lore.kernel.org/all/CAMuHMdXud_RpWag_hFqa2ByBGRxg6KnxGL1ObCWZrpTsk3TfAw@mail.gmail.com/ Fixes:9764e731ef("tracepoint: Add lockdep rcu_is_watching() check to trace_##name##_enabled()") Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
130 lines
3.5 KiB
C
130 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* preemptoff and irqoff tracepoints
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*
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* Copyright (C) Joel Fernandes (Google) <joel@joelfernandes.org>
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*/
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#include <linux/kallsyms.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#include <linux/kprobes.h>
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#include <linux/hardirq.h>
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#include "trace.h"
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#define CREATE_TRACE_POINTS
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#include <trace/events/preemptirq.h>
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/*
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* Use regular trace points on architectures that implement noinstr
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* tooling: these calls will only happen with RCU enabled, which can
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* use a regular tracepoint.
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*
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* On older architectures, RCU may not be watching in idle. In that
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* case, wake up RCU to watch while calling the tracepoint. These
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* aren't NMI-safe - so exclude NMI contexts:
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*/
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#ifdef CONFIG_ARCH_WANTS_NO_INSTR
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#define trace(point, args) trace_##point(args)
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#else
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#define trace(point, args) \
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do { \
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if (__trace_##point##_enabled()) { \
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bool exit_rcu = false; \
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if (in_nmi()) \
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break; \
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if (!IS_ENABLED(CONFIG_TINY_RCU) && \
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is_idle_task(current)) { \
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ct_irq_enter(); \
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exit_rcu = true; \
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} \
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trace_##point(args); \
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if (exit_rcu) \
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ct_irq_exit(); \
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} \
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} while (0)
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#endif
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#ifdef CONFIG_TRACE_IRQFLAGS
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/* Per-cpu variable to prevent redundant calls when IRQs already off */
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static DEFINE_PER_CPU(int, tracing_irq_cpu);
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/*
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* Like trace_hardirqs_on() but without the lockdep invocation. This is
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* used in the low level entry code where the ordering vs. RCU is important
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* and lockdep uses a staged approach which splits the lockdep hardirq
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* tracking into a RCU on and a RCU off section.
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*/
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void trace_hardirqs_on_prepare(void)
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{
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if (this_cpu_read(tracing_irq_cpu)) {
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trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
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tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
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this_cpu_write(tracing_irq_cpu, 0);
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}
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}
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EXPORT_SYMBOL(trace_hardirqs_on_prepare);
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NOKPROBE_SYMBOL(trace_hardirqs_on_prepare);
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void trace_hardirqs_on(void)
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{
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if (this_cpu_read(tracing_irq_cpu)) {
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trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
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tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
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this_cpu_write(tracing_irq_cpu, 0);
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}
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lockdep_hardirqs_on_prepare();
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lockdep_hardirqs_on(CALLER_ADDR0);
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}
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EXPORT_SYMBOL(trace_hardirqs_on);
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NOKPROBE_SYMBOL(trace_hardirqs_on);
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/*
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* Like trace_hardirqs_off() but without the lockdep invocation. This is
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* used in the low level entry code where the ordering vs. RCU is important
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* and lockdep uses a staged approach which splits the lockdep hardirq
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* tracking into a RCU on and a RCU off section.
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*/
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void trace_hardirqs_off_finish(void)
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{
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if (!this_cpu_read(tracing_irq_cpu)) {
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this_cpu_write(tracing_irq_cpu, 1);
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tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1);
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trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
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}
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}
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EXPORT_SYMBOL(trace_hardirqs_off_finish);
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NOKPROBE_SYMBOL(trace_hardirqs_off_finish);
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void trace_hardirqs_off(void)
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{
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lockdep_hardirqs_off(CALLER_ADDR0);
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if (!this_cpu_read(tracing_irq_cpu)) {
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this_cpu_write(tracing_irq_cpu, 1);
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tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1);
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trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
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}
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}
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EXPORT_SYMBOL(trace_hardirqs_off);
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NOKPROBE_SYMBOL(trace_hardirqs_off);
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#endif /* CONFIG_TRACE_IRQFLAGS */
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#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
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void trace_preempt_on(unsigned long a0, unsigned long a1)
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{
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trace(preempt_enable, TP_ARGS(a0, a1));
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tracer_preempt_on(a0, a1);
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}
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void trace_preempt_off(unsigned long a0, unsigned long a1)
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{
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trace(preempt_disable, TP_ARGS(a0, a1));
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tracer_preempt_off(a0, a1);
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}
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#endif
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