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| author | Joel Fernandes (Google) <joel@joelfernandes.org> | 2018-08-05 20:40:49 -0700 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-08-06 21:55:24 -0400 |
| commit | da5b3ebb4527733299661229a8d035d64a4f0b1a (patch) | |
| tree | e422ae6632fd0d11e45e2f0b889b89a7dac0b09c /kernel/trace | |
| parent | da25a672cf0e2c143bffb40acb507a342e25b4f4 (diff) | |
| download | linux-da5b3ebb4527733299661229a8d035d64a4f0b1a.tar.bz2 | |
tracing: irqsoff: Account for additional preempt_disable
Recently we tried to make the preemptirqsoff tracer to use irqsoff
tracepoint probes. However this causes issues as reported by Masami:
[2.271078] Testing tracer preemptirqsoff: .. no entries found ..FAILED!
[2.381015] WARNING: CPU: 0 PID: 1 at /home/mhiramat/ksrc/linux/kernel/
trace/trace.c:1512 run_tracer_selftest+0xf3/0x154
This is due to the tracepoint code increasing the preempt nesting count
by calling an additional preempt_disable before calling into the
preemptoff tracer which messes up the preempt_count() check in
tracer_hardirqs_off.
To fix this, make the irqsoff tracer probes balance the additional outer
preempt_disable with a preempt_enable_notrace.
The other way to fix this is to just use SRCU for all tracepoints.
However we can't do that because we can't use NMIs from RCU context.
Link: http://lkml.kernel.org/r/20180806034049.67949-1-joel@joelfernandes.org
Fixes: c3bc8fd637a9 ("tracing: Centralize preemptirq tracepoints and unify their usage")
Fixes: e6753f23d961 ("tracepoint: Make rcuidle tracepoint callers use SRCU")
Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/trace_irqsoff.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index 770cd30cda40..ffbf1505d5bc 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -603,14 +603,40 @@ static void irqsoff_tracer_stop(struct trace_array *tr) */ static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1) { + /* + * Tracepoint probes are expected to be called with preempt disabled, + * We don't care about being called with preempt disabled but we need + * to know in the future if that changes so we can remove the next + * preempt_enable. + */ + WARN_ON_ONCE(!preempt_count()); + + /* Tracepoint probes disable preemption atleast once, account for that */ + preempt_enable_notrace(); + if (!preempt_trace() && irq_trace()) stop_critical_timing(a0, a1); + + preempt_disable_notrace(); } static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1) { + /* + * Tracepoint probes are expected to be called with preempt disabled, + * We don't care about being called with preempt disabled but we need + * to know in the future if that changes so we can remove the next + * preempt_enable. + */ + WARN_ON_ONCE(!preempt_count()); + + /* Tracepoint probes disable preemption atleast once, account for that */ + preempt_enable_notrace(); + if (!preempt_trace() && irq_trace()) start_critical_timing(a0, a1); + + preempt_disable_notrace(); } static int irqsoff_tracer_init(struct trace_array *tr) |