trace_hardirqs_on/off() is only partially safe vs. RCU idle. The tracer
core itself is safe, but the resulting tracepoints can be utilized by
e.g. BPF which is unsafe.
Provide variants which do not contain the lockdep invocation so the lockdep
and tracer invocations can be split at the call site and placed properly.
The new variants also do not use rcuidle as they are going to be called
from entry code after/before context tracking.
Signed-off-by: Thomas Gleixner <[email protected]>
---
V2: New patch
---
include/linux/irqflags.h | 4 ++++
kernel/trace/trace_preemptirq.c | 23 +++++++++++++++++++++++
2 files changed, 27 insertions(+)
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -29,6 +29,8 @@
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
+ extern void __trace_hardirqs_on(void);
+ extern void __trace_hardirqs_off(void);
extern void trace_hardirqs_on(void);
extern void trace_hardirqs_off(void);
# define trace_hardirq_context(p) ((p)->hardirq_context)
@@ -52,6 +54,8 @@ do { \
current->softirq_context--; \
} while (0)
#else
+# define __trace_hardirqs_on() do { } while (0)
+# define __trace_hardirqs_off() do { } while (0)
# define trace_hardirqs_on() do { } while (0)
# define trace_hardirqs_off() do { } while (0)
# define trace_hardirq_context(p) 0
--- a/kernel/trace/trace_preemptirq.c
+++ b/kernel/trace/trace_preemptirq.c
@@ -19,6 +19,17 @@
/* Per-cpu variable to prevent redundant calls when IRQs already off */
static DEFINE_PER_CPU(int, tracing_irq_cpu);
+void __trace_hardirqs_on(void)
+{
+ if (this_cpu_read(tracing_irq_cpu)) {
+ if (!in_nmi())
+ trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1);
+ tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
+ this_cpu_write(tracing_irq_cpu, 0);
+ }
+}
+NOKPROBE_SYMBOL(__trace_hardirqs_on);
+
void trace_hardirqs_on(void)
{
if (this_cpu_read(tracing_irq_cpu)) {
@@ -33,6 +44,18 @@ void trace_hardirqs_on(void)
EXPORT_SYMBOL(trace_hardirqs_on);
NOKPROBE_SYMBOL(trace_hardirqs_on);
+void __trace_hardirqs_off(void)
+{
+ if (!this_cpu_read(tracing_irq_cpu)) {
+ this_cpu_write(tracing_irq_cpu, 1);
+ tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1);
+ if (!in_nmi())
+ trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1);
+ }
+
+}
+NOKPROBE_SYMBOL(__trace_hardirqs_off);
+
void trace_hardirqs_off(void)
{
if (!this_cpu_read(tracing_irq_cpu)) {
On 3/8/20 11:24 PM, Thomas Gleixner wrote:
> trace_hardirqs_on/off() is only partially safe vs. RCU idle. The tracer
> core itself is safe, but the resulting tracepoints can be utilized by
> e.g. BPF which is unsafe.
>
> Provide variants which do not contain the lockdep invocation so the lockdep
> and tracer invocations can be split at the call site and placed properly.
>
> The new variants also do not use rcuidle as they are going to be called
> from entry code after/before context tracking.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> ---
> V2: New patch
> ---
> include/linux/irqflags.h | 4 ++++
> kernel/trace/trace_preemptirq.c | 23 +++++++++++++++++++++++
> 2 files changed, 27 insertions(+)
>
> --- a/include/linux/irqflags.h
> +++ b/include/linux/irqflags.h
> @@ -29,6 +29,8 @@
> #endif
>
> #ifdef CONFIG_TRACE_IRQFLAGS
> + extern void __trace_hardirqs_on(void);
> + extern void __trace_hardirqs_off(void);
> extern void trace_hardirqs_on(void);
> extern void trace_hardirqs_off(void);
> # define trace_hardirq_context(p) ((p)->hardirq_context)
> @@ -52,6 +54,8 @@ do { \
> current->softirq_context--; \
> } while (0)
> #else
> +# define __trace_hardirqs_on() do { } while (0)
> +# define __trace_hardirqs_off() do { } while (0)
> # define trace_hardirqs_on() do { } while (0)
> # define trace_hardirqs_off() do { } while (0)
> # define trace_hardirq_context(p) 0
> --- a/kernel/trace/trace_preemptirq.c
> +++ b/kernel/trace/trace_preemptirq.c
> @@ -19,6 +19,17 @@
> /* Per-cpu variable to prevent redundant calls when IRQs already off */
> static DEFINE_PER_CPU(int, tracing_irq_cpu);
>
> +void __trace_hardirqs_on(void)
> +{
> + if (this_cpu_read(tracing_irq_cpu)) {
> + if (!in_nmi())
> + trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1);
> + tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
> + this_cpu_write(tracing_irq_cpu, 0);
> + }
> +}
> +NOKPROBE_SYMBOL(__trace_hardirqs_on);
> +
Shouldn't trace_hardirqs_on() be updated to call __trace_hardirqs_on()? It's the same
code except for the lockdep call.
void trace_hardirqs_on(void)
{
__trace_hardirqs_on();
lockdep_hardirqs_on(CALLER_ADDR0);
}
EXPORT_SYMBOL(trace_hardirqs_on);
NOKPROBE_SYMBOL(trace_hardirqs_on);
> void trace_hardirqs_on(void)
> {
> if (this_cpu_read(tracing_irq_cpu)) {
> @@ -33,6 +44,18 @@ void trace_hardirqs_on(void)
> EXPORT_SYMBOL(trace_hardirqs_on);
> NOKPROBE_SYMBOL(trace_hardirqs_on);
>
> +void __trace_hardirqs_off(void)
> +{
> + if (!this_cpu_read(tracing_irq_cpu)) {
> + this_cpu_write(tracing_irq_cpu, 1);
> + tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1);
> + if (!in_nmi())
> + trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1);
> + }
> +
> +}
> +NOKPROBE_SYMBOL(__trace_hardirqs_off);
> +
Same comment here.
alex.
> void trace_hardirqs_off(void)
> {
> if (!this_cpu_read(tracing_irq_cpu)) {
>
On Tue, Mar 10, 2020 at 11:55:57AM +0100, Alexandre Chartre wrote:
> Shouldn't trace_hardirqs_on() be updated to call __trace_hardirqs_on()? It's the same
> code except for the lockdep call.
Fell into that one too initially. Look again. :)
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On 3/10/20 12:08 PM, Borislav Petkov wrote:
> On Tue, Mar 10, 2020 at 11:55:57AM +0100, Alexandre Chartre wrote:
>> Shouldn't trace_hardirqs_on() be updated to call __trace_hardirqs_on()? It's the same
>> code except for the lockdep call.
>
> Fell into that one too initially. Look again. :)
>
Got it, rcuidle :) So maybe a better function name or a comment could avoid
this confusion.
Anyway, Reviewed-by: Alexandre Chartre <[email protected]>
alex.