[for-next][PATCH 17/21] rv/monitor: Add the wip monitor

From: Steven Rostedt
Date: Sun Jul 31 2022 - 15:05:37 EST

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From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>

The wakeup in preemptive (wip) monitor verifies if the
wakeup events always take place with preemption disabled:

|
|
v
#==================#
H preemptive H <+
#==================# |
| |
| preempt_disable | preempt_enable
v |
sched_waking +------------------+ |
+--------------- | | |
| | non_preemptive | |
+--------------> | | -+
+------------------+

The wakeup event always takes place with preemption disabled because
of the scheduler synchronization. However, because the preempt_count
and its trace event are not atomic with regard to interrupts, some
inconsistencies might happen.

The documentation illustrates one of these cases.

Link: https://lkml.kernel.org/r/c98ca678df81115fddc04921b3c79720c836b18f.1659052063.git.bristot@xxxxxxxxxx

Cc: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: Gabriele Paoloni <gpaoloni@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Clark Williams <williams@xxxxxxxxxx>
Cc: Tao Zhou <tao.zhou@xxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-trace-devel@xxxxxxxxxxxxxxx
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
Documentation/trace/rv/index.rst | 1 +
Documentation/trace/rv/monitor_wip.rst | 55 ++++++++++++++++++++++++++
include/trace/events/rv.h | 10 +++++
kernel/trace/rv/Kconfig | 13 ++++++
kernel/trace/rv/Makefile | 1 +
kernel/trace/rv/monitors/wip/wip.c | 51 +++++++-----------------
tools/verification/models/wip.dot | 16 ++++++++
7 files changed, 111 insertions(+), 36 deletions(-)
create mode 100644 Documentation/trace/rv/monitor_wip.rst
create mode 100644 tools/verification/models/wip.dot

diff --git a/Documentation/trace/rv/index.rst b/Documentation/trace/rv/index.rst
index db2ae3f90b90..4cb71ed628b8 100644
--- a/Documentation/trace/rv/index.rst
+++ b/Documentation/trace/rv/index.rst
@@ -10,3 +10,4 @@ Runtime Verification
deterministic_automata.rst
da_monitor_synthesis.rst
da_monitor_instrumentation.rst
+ monitor_wip.rst
diff --git a/Documentation/trace/rv/monitor_wip.rst b/Documentation/trace/rv/monitor_wip.rst
new file mode 100644
index 000000000000..a95763438c48
--- /dev/null
+++ b/Documentation/trace/rv/monitor_wip.rst
@@ -0,0 +1,55 @@
+Monitor wip
+===========
+
+- Name: wip - wakeup in preemptive
+- Type: per-cpu deterministic automaton
+- Author: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
+
+Description
+-----------
+
+The wakeup in preemptive (wip) monitor is a sample per-cpu monitor
+that verifies if the wakeup events always take place with
+preemption disabled::
+
+ |
+ |
+ v
+ #==================#
+ H preemptive H <+
+ #==================# |
+ | |
+ | preempt_disable | preempt_enable
+ v |
+ sched_waking +------------------+ |
+ +--------------- | | |
+ | | non_preemptive | |
+ +--------------> | | -+
+ +------------------+
+
+The wakeup event always takes place with preemption disabled because
+of the scheduler synchronization. However, because the preempt_count
+and its trace event are not atomic with regard to interrupts, some
+inconsistencies might happen. For example::
+
+ preempt_disable() {
+ __preempt_count_add(1)
+ -------> smp_apic_timer_interrupt() {
+ preempt_disable()
+ do not trace (preempt count >= 1)
+
+ wake up a thread
+
+ preempt_enable()
+ do not trace (preempt count >= 1)
+ }
+ <------
+ trace_preempt_disable();
+ }
+
+This problem was reported and discussed here:
+ https://lore.kernel.org/r/cover.1559051152.git.bristot@xxxxxxxxxx/
+
+Specification
+-------------
+Grapviz Dot file in tools/verification/models/wip.dot
diff --git a/include/trace/events/rv.h b/include/trace/events/rv.h
index 20a2e09c6416..e972f27d8df3 100644
--- a/include/trace/events/rv.h
+++ b/include/trace/events/rv.h
@@ -56,6 +56,16 @@ DECLARE_EVENT_CLASS(error_da_monitor,
__entry->event,
__entry->state)
);
+
+#ifdef CONFIG_RV_MON_WIP
+DEFINE_EVENT(event_da_monitor, event_wip,
+ TP_PROTO(char *state, char *event, char *next_state, bool final_state),
+ TP_ARGS(state, event, next_state, final_state));
+
+DEFINE_EVENT(error_da_monitor, error_wip,
+ TP_PROTO(char *state, char *event),
+ TP_ARGS(state, event));
+#endif /* CONFIG_RV_MON_WIP */
#endif /* CONFIG_DA_MON_EVENTS_IMPLICIT */

#ifdef CONFIG_DA_MON_EVENTS_ID
diff --git a/kernel/trace/rv/Kconfig b/kernel/trace/rv/Kconfig
index 0d9552b406c6..e50f3346164a 100644
--- a/kernel/trace/rv/Kconfig
+++ b/kernel/trace/rv/Kconfig
@@ -25,6 +25,19 @@ menuconfig RV
For further information, see:
Documentation/trace/rv/runtime-verification.rst

+config RV_MON_WIP
+ depends on RV
+ depends on PREEMPT_TRACER
+ select DA_MON_EVENTS_IMPLICIT
+ bool "wip monitor"
+ help
+ Enable wip (wakeup in preemptive) sample monitor that illustrates
+ the usage of per-cpu monitors, and one limitation of the
+ preempt_disable/enable events.
+
+ For further information, see:
+ Documentation/trace/rv/monitor_wip.rst
+
config RV_REACTORS
bool "Runtime verification reactors"
default y
diff --git a/kernel/trace/rv/Makefile b/kernel/trace/rv/Makefile
index 8944274d9b41..b41109d2750a 100644
--- a/kernel/trace/rv/Makefile
+++ b/kernel/trace/rv/Makefile
@@ -2,3 +2,4 @@

obj-$(CONFIG_RV) += rv.o
obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
+obj-$(CONFIG_RV_MON_WIP) += monitors/wip/wip.o
diff --git a/kernel/trace/rv/monitors/wip/wip.c b/kernel/trace/rv/monitors/wip/wip.c
index 79a054ca0cde..83cace53b9fa 100644
--- a/kernel/trace/rv/monitors/wip/wip.c
+++ b/kernel/trace/rv/monitors/wip/wip.c
@@ -10,44 +10,26 @@

#define MODULE_NAME "wip"

-/*
- * XXX: include required tracepoint headers, e.g.,
- * #include <linux/trace/events/sched.h>
- */
#include <trace/events/rv.h>
+#include <trace/events/sched.h>
+#include <trace/events/preemptirq.h>

-/*
- * This is the self-generated part of the monitor. Generally, there is no need
- * to touch this section.
- */
#include "wip.h"

-/*
- * Declare the deterministic automata monitor.
- *
- * The rv monitor reference is needed for the monitor declaration.
- */
struct rv_monitor rv_wip;
DECLARE_DA_MON_PER_CPU(wip, unsigned char);

-/*
- * This is the instrumentation part of the monitor.
- *
- * This is the section where manual work is required. Here the kernel events
- * are translated into model's event.
- *
- */
-static void handle_preempt_disable(void *data, /* XXX: fill header */)
+static void handle_preempt_disable(void *data, unsigned long ip, unsigned long parent_ip)
{
da_handle_event_wip(preempt_disable_wip);
}

-static void handle_preempt_enable(void *data, /* XXX: fill header */)
+static void handle_preempt_enable(void *data, unsigned long ip, unsigned long parent_ip)
{
- da_handle_event_wip(preempt_enable_wip);
+ da_handle_start_event_wip(preempt_enable_wip);
}

-static void handle_sched_waking(void *data, /* XXX: fill header */)
+static void handle_sched_waking(void *data, struct task_struct *task)
{
da_handle_event_wip(sched_waking_wip);
}
@@ -60,9 +42,9 @@ static int enable_wip(void)
if (retval)
return retval;

- rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
- rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
- rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
+ rv_attach_trace_probe("wip", preempt_enable, handle_preempt_enable);
+ rv_attach_trace_probe("wip", sched_waking, handle_sched_waking);
+ rv_attach_trace_probe("wip", preempt_disable, handle_preempt_disable);

return 0;
}
@@ -71,19 +53,16 @@ static void disable_wip(void)
{
rv_wip.enabled = 0;

- rv_detach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
- rv_detach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
- rv_detach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
+ rv_detach_trace_probe("wip", preempt_disable, handle_preempt_disable);
+ rv_detach_trace_probe("wip", preempt_enable, handle_preempt_enable);
+ rv_detach_trace_probe("wip", sched_waking, handle_sched_waking);

da_monitor_destroy_wip();
}

-/*
- * This is the monitor register section.
- */
struct rv_monitor rv_wip = {
.name = "wip",
- .description = "auto-generated wip",
+ .description = "wakeup in preemptive per-cpu testing monitor.",
.enable = enable_wip,
.disable = disable_wip,
.reset = da_monitor_reset_all_wip,
@@ -105,5 +84,5 @@ module_init(register_wip);
module_exit(unregister_wip);

MODULE_LICENSE("GPL");
-MODULE_AUTHOR("dot2k: auto-generated");
-MODULE_DESCRIPTION("wip");
+MODULE_AUTHOR("Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>");
+MODULE_DESCRIPTION("wip: wakeup in preemptive - per-cpu sample monitor.");
diff --git a/tools/verification/models/wip.dot b/tools/verification/models/wip.dot
new file mode 100644
index 000000000000..2a53a9700a89
--- /dev/null
+++ b/tools/verification/models/wip.dot
@@ -0,0 +1,16 @@
+digraph state_automaton {
+ {node [shape = circle] "non_preemptive"};
+ {node [shape = plaintext, style=invis, label=""] "__init_preemptive"};
+ {node [shape = doublecircle] "preemptive"};
+ {node [shape = circle] "preemptive"};
+ "__init_preemptive" -> "preemptive";
+ "non_preemptive" [label = "non_preemptive"];
+ "non_preemptive" -> "non_preemptive" [ label = "sched_waking" ];
+ "non_preemptive" -> "preemptive" [ label = "preempt_enable" ];
+ "preemptive" [label = "preemptive"];
+ "preemptive" -> "non_preemptive" [ label = "preempt_disable" ];
+ { rank = min ;
+ "__init_preemptive";
+ "preemptive";
+ }
+}
--
2.35.1

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